Thomas Aquinas on Dreams

Thomas Aquinas on dreams. Harm Goris Abstract: Thomas Aquinas adopts and adapts the Aristotelian natural explanations of dreams within a Christian theological context. He offers no interpretations of particular dream stories, but develops a theory about dreams, in particular about their prognostic value. A dream can predict a future event if it is caused by something that either also causes the future event or has knowledge of that event. Aquinas makes a fourfold classification of causes of dreams and indicates how each of these causes can relate to specific future events. The four causes are divided between internal-external and physical-spiritual causes. First, an internal, psychological preoccupation can cause a specific dream and thereby give the dreamer the incentive to a specific future action. Second, internal physiological processes can influence our dreams and also determine future health conditions. Third, external physical causes of dreams are the celestial bodies, which also exercise causal influence on e.g. future meteorological circumstances. Finally, external spiritual agents, demons and God (through the mediation of good angels), can send dreams, while they also can cause or know future events. While acknowledging the possibility of prognostications in dreams through physical causes and of divine prophecy in dreams, Aquinas remains rather pessimistic about the frequency of such predictive dreams: it is much more probable that prognostic dreams are sent by demons. As a magister in sacra pagina, a master of the Sacred Page, the first task of Thomas Aquinas (1224/5 – 1274) was to explain Scripture. He did so not only in the specific literary genre of the biblical commentary, but also in his systematic writings, e.g. in his most influential work, the Summa Theologiae, which was written between 1265 and 1274 but remained incomplete.1 Also when Aquinas expounds his systematic views on dreams, Scripture plays a fundamental role. The biblical view on dreams is ambivalent.2 On the one hand, dreams serve to convey divine messages. God is said to give people warnings and predictions through dreams. He himself declares to Moses: ‘When there are prophets among you, I the Lord 1 The best biography of Thomas Aquinas is: Jean-Pierre Torrell, Initiation à saint Thomas d’Aquin. Sa personne et son oeuvre (Paris, 22002), translated into English by Robert Royal as Saint Thomas Aquinas. Vol. 1, The Person and His Works (Washington, 2005). Volumes of a critical edition of Aquinas’ complete works have been published by the so-called Leonine Committee since 1882. The most widely used edition of the Summa Theologiae (hereafter cited as S.Th.) is the Blackfriars edition: Summa Theologiae: Latin text and English translation, introductions, notes, appendices, and glossaries, 60 vols (London, 1964-1976). The complete works in Latin are online available on a website maintained by Enrique Alarcón: www.corpusthomisticum.org. 2 See the introduction to this volume by Bart Koet. 1 make myself known to them in visions; I speak to them in dreams’ (Num 12:6). Examples of such divine revelations can be found in the stories in the book of Genesis about Jacob dreaming in Bethel and the dreams of Joseph and of Pharaoh, in the book of Daniel, who interprets the dreams of king Nebuchadnezzar. Also Job 33: 15-16 states that God communicates with people nighttime dreams. In the gospels we find the warning dreams that alert the Magi and Joseph after the birth of Jesus for the wrath of King Herod, and there is the dream of Pilate’s wife. On the other hand, Scripture is also cautious about putting too much faith in dreams. They can be vain and fleeting, as is said in Ecclesiastes: ‘dreams come with many cares, and a fool’s voice with many words’ (5:3) and ‘with many dreams come vanities and a multitude of words’ (5:7). A similar dissuasion is given in Isaiah 29:7-8. We find also more serious admonitions against the dreams of false prophets (Deut 13: 1-5; Jer 23:25-32, 27:9 and 29:8-9): heeding their messages is not just foolish, it is idolatry. Thomas Aquinas is aware of the different attitudes towards dreams in Scripture. In Summa Theologiae IIa-IIae question 95, article 6, his main text on dreams, we find quotations from Num 12, Job 33 and references to the dream explanations by Joseph and Daniel, while the prohibition of dream divination in Deut 18: 10 hints at Aquinas’ own basic attitude.3 Also during the patristic period and the early Middle Ages, we find both positive and more cautious views on dreams.4 Theological suspicion of dreams was fuelled again in the twelfth and thirteenth century with the rediscovery of Aristotle’s writing and the introduction of his empirical- rational approach at the newly founded universities in Europe. In the early 1200s, three biological works in which Aristotle discusses dreams were translated into Latin: On Sleep, On Dreams, and On Divination in Sleep.5 In these texts Aristotle argues for natural explanations of dreams in terms of physiological and psychological processes, and he is very negative about the possibility of dreams being sent by God for predicting the future. Sometimes dreams may seem to come true, but that does not prove that they are of supernatural origin. It may just be a coincidence, or otherwise the dream itself is the cause of the future event, or both the dream and the event predicted in it can be traced back to a common natural cause, which may be unknown. In the last-mentioned case, the dream is said to be a ‘sign’ of the future event. Moreover, Aristotle argues, it does not seem reasonable that God would send dreams to inferior people, who are more prone to dreams, or even to animals, who also dream. And, finally, the most important 3 Aquinas uses the Vulgate text, which he quotes as: ‘Non inveniatur in te qui observet somnia’ (‘Let no one be found among you who observes dreams’). The original Hebrew text does not speak about ‘dreams’. 4 See other contributions in this volume and Guy Stroumsa, ‘Dreams and Visions in Early Christian Discourse,’ in David Shulman and Guy G. Stroumsa (eds), Dream Cultures. Explorations in the Comparative History of Dreaming (New York, 1999) 189-212. 5 A good introduction into Aristotle’s dream theory is the introduction by David Gallop in: Aristotle, On Sleep and Dreams. A Text and Translation with Introduction, Notes and Glossary (Warminster, 1996) 1-57. On these translations and their early reception, see: Thomas Ricklin, Der Traum der Philosophie im 12. Jahrhundert. Traumtheorien zwischen Constantinus Africanus und Aristoteles (Leiden etc., 1998) 323-408. 2 consideration for Aristotle is that he holds to an open, indeterminate future, which logically excludes the possibility of infallible predictions of future chance events. He does not mention this argument explicitly in On Divination in Sleep. However, he gives ‘a sea battle’ as an example of a chance event (463b1). This echoes the sample sentence in his famous discussion on future contingents in On Interpretation: ‘Tomorrow there will be a sea battle’, where it is argued that such a sentence is neither true, nor is it false.6 In On Divination in Sleep Aristotle concludes: On the whole, forasmuch as certain of the other animals also dream, it may be concluded that dreams are not sent by God, nor are they designed for this purpose. They have a mysterious aspect, however, for nature is mysterious, though not divine. A sign is this: the power of foreseeing the future and of having vivid dreams is found in persons of inferior type, which implies that God does not send their dreams; but merely that all those whose physical temperament is, as it were, garrulous and melancholic, see sights of all descriptions.7 Thirteenth-century Christian scholars reacted differently to Aristotle’s one-sided, negative verdict on divinatory dreams. Steven Kruger has argued convincingly that some of them adhered to a ‘relatively pure Aristotelian dream theory’, like e.g. Boethius of Dacia and Adam of Buckfield, either ignoring or maybe even denying the possibility of God sent dreams. However, most scholastic writers adopted and at the same time also adapted Aristotle’s explanation of dreams. They changed and amplified the Aristotelian dream theory so that it would become consistent with scriptural and patristic sources. Kruger shows this to be the case for a number of authors. He discusses in particular the dream theory of Aquinas’ teacher, Albert the Great.8 However, Kruger does not treat Thomas Aquinas’ view on dreams. On the other hand, Morton Kelsey concluded after analyzing Aquinas’ texts on dreams that ‘… there is no place for dreams either in the philosophic system of Aristotle or in the theology of Aquinas.’9 If Kelsey is right, this would mean that Aquinas belongs to Kruger’s group of authors that fully accepted Aristotle’s negative view on dreams. In this contribution I shall describe and analyze the view of Thomas Aquinas on dreams and on their prognostic value. The conclusion will be that Kelsey’s judgment is incorrect and that Aquinas modifies and expands Aristotle’s dream theory. Unlike his master Albert the Great, Aquinas does not treat of dreams very extensively. The longest and most detailed text is Summa Theologiae IIa-IIae question 95, article 6. The context is a more general discussion on the permissibility of divination through 6 Aristotle, On Interpretation c. 9. 7 Aristotle, On Divination in Sleep, c. 2, 463b11-18. The Complete Works of Aristotle. The Revised Oxford Translation, ed. Jonathan Barnes (Princeton, 1984) vol. 1, 737. 8 Steven Kruger, Dreaming in the Middle Ages (Cambridge, 1992) 99-113. 9 Morton T. Kelsey, God, Dreams and Revelation. A Christian Interpretation of Dreams (Minneapolis, 1974) 173-78, quotation on 175. 3 demons (article 4), stars (article 5), auguries like the flight of birds (article 7) and casting lots (article 8). Most other discussions on dreams in Aquinas’ works also occur in the context of prophecy and divination. With very few exceptions, Aquinas’ discussions of dreams are always from a theoretical viewpoint. He offers considerations about scientific, philosophical and theological aspects of dreams in general, but does not relate concrete dream stories or give interpretations of the content of individual dreams. Only in his biblical commentaries, we find some short comments on particular dreams, like the ones of Pilate’s wife and of Joseph in the gospel of Matthew. The structure of my paper will follow closely the text in Summa Theologiae IIa- IIae question 95, article 6. The text is organized in such a way that it allows for a clear, over-all survey of Aquinas’ dream theory. I shall analyze Aquinas’ arguments, drawing additional information from other passages in his works. 1. Ambivalence of predictive dreams Aquinas’ discussion whether oneiromancy is allowed in Summa Theologiae IIa-IIae qu. 95 art. 6 follows the dialectical structure of the medieval genre of the quaestio, reflecting at the same time the traditional ambivalent attitude of theologians towards dreams. Three reasons are listed why divination through dreams is allowed. First, Scripture says that God himself instructs people in dreams.10 Aquinas refers to Job 33:15-16 as evidence: ‘In a dream, in a vision of the night, when deep sleep falls on mortals, while they slumber on their beds, then he opens their ears, and terrifies them with warnings.’ The next argument is implicitly directed against Aristotle’s claim that inferior persons have the most vivid dreams about the future. Scripture reports that holy men like Joseph and Daniel have interpreted dreams. And finally, it is a common human experience that dreams signify something about the future, and it would be unreasonable to deny such experiences. Against these three arguments, the prohibition is brought in from Deut. 18:10, ‘No one shall be found among who observes dreams’ as counterargument or sed contra. 2. Divination and prophecy As usual in a quaestio, Aquinas’ own position is in line with the sed contra. He begins his answer to the problem as follows: I answer that, as was said before, divination, which is based on a false opinion, is superstitious and unlawful. Aquinas refers to what he had said about divination in previous articles in Summa Theologiae IIa-IIae question 95. He thinks that divination in the strict sense is always a sinful and unlawful act for by definition it concerns unduly usurping a divine prerogative, viz. the foretelling of future chance events.11 Moreover, divination as such 10 S.Th. IIa-IIae q. 95 a. 6 ob. 1. 11 S.Th. IIa-IIae q. 95 a. 1. 4 always happens through the activity of demons, ‘either because people invoke them expressly to disclose the future, or because the demons invade people’s futile probing into the future so that they entangle the minds of these people through their vanity.’12 This conception of divination does not deny the possibility that dreams are sent by God and reveal truly and lawfully future chance events. However, such a God-given dream would not be a matter of divination. It would not be the usurpation of a divine prerogative, but the reception of a God-given charisma. Playing on the verbal similarity between ‘to divine’ (divinare) and ‘divine’ (divinum), Aquinas says that in the case of dream prophecy ‘a person does not divine, that is that he does something divine, but rather he receives it.’13 Therefore, what Joseph and Daniel did when they foretold the future from the dreams of Pharaoh and King Nebuchadnezzar, was properly speaking not divination. Elsewhere, Aquinas makes clear that it was prophecy. Prophecy through a dream (somnium) in sleep, he says, is a proper form of prophecy and deals with ‘supernatural truth’, which cannot be known in any natural way, though it is inferior compared to other forms of prophecy, viz. prophecy through a vision (visio), which occurs in the state of wakefulness, or purely intellectual prophecy without any images whatsoever.14 However, following Aristotle, Aquinas had also referred to the common experience and belief of people that dreams can show something about the future. How does Aquinas deal with this phenomenon? After all, it cannot be explained in terms of divinely inspired prophecy, which is a rare event. 3. Dreams causing and dreams signifying the future Aquinas continues and follows Aristotle in distinguishing between dreams as causes and dreams as signs of future events. Dreams can cause the events that they depict for they can incite people to act in a certain way. Therefore, we have to examine what is true about the precognition of future events on the basis of dreams. Sometimes dreams are the cause of future events: for example, when the mind of someone, worried because of what he saw in dreams, is led to do something or refrain from it. The more common and more interesting case, as Aristotle had already pointed out, is that a dream is not a cause but a sign of a future event. 12 S.Th. IIa-IIae q. 95 a. 2. 13 Ibid.: ‘… tunc enim non ipse divinat, idest, quod divinum est facit, sed magis quod divinum est suscipit’ (‘… for then he does not divine, that is, does something which is divine, but rather receives something that is divine’). 14 S.Th.IIa-IIae q. 174 a. 3. See also De Veritate q. 12 a. 3 and 13 (Opera Omnia, Leonine edition vol. 22.2 [Rome, 1972] 377, 411). Aquinas sees this division between a dream and a vision reflected in Num 12:6, which he paraphrases as distinguishing between ‘a dream’ (somnium) and ‘a vision of wakefulness’ (visio vigiliae), though the term ‘wakefulness’ is neither found in the Hebrew text, nor in the Vulgate: De Veritate q. 12 a. 13. 5  Sometimes, however, dreams are signs of certain future events, insofar as they are reduced to some cause that is common to the dreams and the future events. This is how most precognitions of the future on the basis of dreams happen. Therefore, we have to examine what the cause is of dreams; and if that cause can also be the cause of future events, or can know these. A dream can be a sign of a future event in two ways. The first way is that the dream and the future event share a common cause or causes. Earlier, Aquinas had explained that causal relations between a sign and what it signifies are twofold: either that which is signified causes the sign, like smoke (the cause) signifies fire (the effect), or both the sign and that which is signified are effects of the same cause(s).15 The former does not apply here, for backward causation is impossible. An effect cannot precede its cause in time and, therefore, it makes no sense to talk about a future event causing a dream today. The latter is relevant here, viz. the sign and signified share the same cause. Aquinas gives the example of a rainbow ‘which sometimes signifies fair weather, insofar as its cause is also the cause of fair weather’.16 This can also happen in the case of foretelling dreams. It is possible that a dream and the future event that it signifies, are traced back to a common cause. The second way in which a dream can signify something in the future is when that which causes the dream, has knowledge of the future event without actually causing it. Aristotle did not consider this idea in his dream theory, but Aquinas adds it to cover the possibility that God or demons know future events and disclose them to people, without actually causing these events. After all, God knows of future evils, but He does not cause them. Likewise, demons and angels can have knowledge of some future events that are not caused by them. If and how dreams can be signs, Aquinas explains by investigating the different causes of dreams themselves and by examining how each of them relates to future events. Aquinas distinguishes two kinds of causes of dreams: internal and external. Each of these is again subdivided in a material and a spiritual cause.17 The internal material cause of dreams is the body, the internal spiritual cause is the soul. The external material causes of dreams are the direct surroundings of the dreamer and the celestial bodies. The external spiritual causes are demons or God (and good angels). 4. Internal causes: the soul and the body 15S.Th. IIa-IIae q. 95 art 5. 16S.Th. IIa-IIae q. 95 art 5. See also in the Commentary on the Sentences of Peter Lombard - hereafter cited as In Sent. - : In II Sent. d. 15 q. 1 a. 2 ad 1 (Scriptum super libros Sententiarum t. 2, ed. P. Mandonnet [Paris, 1929] 372). 17 The fourfold division of causes of dreams occurs also In II Sent. d. 7 q. 2 a. 2 ad 6 (Scriptum t. 2, 191-192). It also is found in the Commentary on Matthew, c. 27 lc. 1 nr. 2336 (Super Evangelium S. Matthaei Lectura, ed. R. Cai [Turin and Rome, 51951] 360). However, this part of the commentary is not by Aquinas himself; it is a so-called reportatio by a student: see Torrell, Initiation { saint Thomas d’Aquin, 81-83. 6 The text continues as follows: It must be known that the cause of dreams is sometimes internal and sometimes external. The internal cause of dreams is twofold: one is the soul, insofar as those things present themselves to the imagination of a person while asleep, on which his thoughts and emotions lingered while awake. And such a cause of dreams is not the cause of future events. And such dreams have an accidental relation to future events and if they sometimes occur together, it will be by chance. The soul can be the cause of dreams when we have been preoccupied in our thoughts and emotions with particular things during the day. These things can recur in our imagination at night when we are asleep.18 But such mental preoccupations have out of themselves no relationship with particular future events. Therefore, any resemblance between such psychologically caused dream images and later events is purely coincidental, unless the mind is brought to act later in a certain way because of a certain dream. But then we have the case of a dream functioning as a cause, which has been discussed above. Dreams can also be caused by internal bodily processes, Aquinas continues: Sometimes the internal cause of dreams is corporeal. From a certain internal disposition of the body, some change is formed in the imagination, which corresponds to that disposition. As to a person, in whom cold humours predominate, it occurs that he is in the water or in the snow. And that is why medical doctors say that we should pay attention to dreams in order to know our internal dispositions. In the background of this passage is Aquinas’ theory that dreams are rooted in natural physiological processes. He claims that even before the Fall, when human nature was not yet corrupted by sin, Adam and Eve had dreams. 19 Not all of Aquinas’ contemporaries agreed on this. The Franciscan theologian Bonaventure, for example, denied that Adam and Eve had self-induced dreams in Paradise.20 Such dreams, he argued, are deceptive for they depict something that is not real. Therefore, they could not occur in the perfect state of God’s original creation. Only God-given, supernatural dreams could have taken place in Paradise. Aquinas, however, is less negative about our normal natural processes. In his view, they belong to God’s good creation. Therefore, as Adam and Eve enjoyed sexual pleasure before the Fall (even better than after the Fall)21, 18 See also Expositio super Iob c. 4 (Opera Omnia, Leonine edition vol. 26 [Rome, 1965] 30-31). 19 De Veritate q. 18 a. 6 ad 14 and 15 (Opera Omnia vol. 22.2, 554); S.Th. Ia q. 94 a. 4 obi. 4 and ad 4. 20 Bonaventure, Commentaria in Quatuor Libros Sententiarum , book II, d. 23, a. 2, q. 2, ad 4 (Opera Omnia S. Bonaventurae, Quaracchi edition vol. 2 [Ad Claras Aquas, 1885] 541. See also the Summa Theologica, attributed to Alexander of Hales, vol. 1.2, nr. 471 (Quaracchi edition [Ad Claras Aquas, 1928] 638-40). 21 S.Th. Ia q. 98 a. 2 ad 3. 7 urinated and defecated like we do (though without offensiveness)22, they also dreamt. However, Aquinas argues, the unreality of the dream world did not deceive their intellect, as the human intellect is ‘bound’ or blocked during sleep and cannot function and judge freely whether or not the dream images, which belong to the domain of the senses, correspond to reality.23 In short, imagining nonexistent things in dreams is not a matter of deception or of error. What matters according to Aquinas, is the interpretation and assessment of dreams by the intellect. We shall return to this later. Following Aristotle, Aquinas thinks that the natural origin of dreams lies in the vapours and gasses that are released during digestion and in specific movements of the blood during sleep. When we are asleep, the blood ‘descends’, i.e. it moves from the outer sense organs to the inner organ of sense perception, viz. the heart or part of the brains, taking with it the remnants of actual sense-impressions, which change the inner sensory centre, creating the impression as if this centre is moved by the real, outer objects.24 When we are in a very deep sleep, e.g. after a sumptuous meal and much drinking, the gasses move so violently that not only the intellect, but also the internal and the external senses are completely blocked and prevented from functioning properly. One sleeps like a log without dreaming. During the rest of the sleep, the intellect remains blocked and also ‘the external senses remain dull because of the vapours of the sleep that ascend to the brain and immobilize the organ of touch’, which is the basis of all the other outer senses.25 However, gradually, when the motions of the digestive vapours become less forceful, the blood moves more regularly and some internal senses can start to function. This begins with the power of imagination, the function of which is to store impressions received from the outer senses and which can S.Th. Ia q. 97 a. 3 ad 4. 22 In II Sent. d. 19 q. 1 a. 3 ad 3 (Scriptum t. 2, p. 489-490). In De Veritate q. 18 a. 6 ad 14 (Opera 23 Omnia vol. 22.2, 554), Aquinas says that in the case of dreams the deception is not in the intellect, but ‘more in the sensory part.’ However, this would still suggest that deception is part of God’s good creation. Aquinas might not be fully consistent here. 24 Cf. Aristotle, On Dreams, c. 3, 461a1-b24 (Complete Works, vol. 1, 733). Aquinas discusses the physiological basis of dreams in S.Th. Ia q. 84 a. 8 ad 2, q. 111 a. 3; S.Th. Ia-IIae q. 80 a. 2; De Malo q. 3 a. 4 (Opera Omnia, Leonine edition vol. 23 [Rome-Paris, 1982] 76); Expositio super Iob c. 4 (Opera Omnia vol. 26, 30). In In II Sent. d. 19 q. 1 a. 3 ad 3 (Scriptum t. 2, 489), Aquinas mentions the humidity of the brain in very young children as another natural cause for dreams besides food vapours during digestion. This would explain why little children sleep and dream much more than adults. On medieval discussions whether the heart (Aristotle) or part of the brain (Galen, Arabic philosophers) is the inner seat of sense perception, see Simo Knuuttila, ‘Aristotle’s Theory of Perception and Medieval Aristotelianism,’ in S. Knuuttila and P. Kärkkäinen (eds), Theories of Perception in Medieval and Early Modern Philosophy (New York, 2008) 1-22. The heart or the brain as ‘subject of sleep/dream’ is also mentioned by Aquinas in his Commentary on the Metaphysics, book VIII, lect. 4 nr. 1745 (In duodecim libros Metaphysicorum Aristotelis expositio. Ed. M. R. Cathala and R. M. Spiazzi [Turin and Rome, 1950] 416). 25 De Veritate q. 12 a. 9 (Opera Omnia vol. 22.2, 396). See also In de Anima Sentencia II l. 19: ‘tactus est fundamentum omnium aliorum sensuum’ ( ‘touch is the foundation of all other senses’ ), (Opera Omnia, Leonine edition vol. 45.1 [Rome-Paris, 1984] 149). 8 also combine these into purely imaginary representation of e.g. a gold mountain.26 First distorted, as in fever dreams, but then more coherent sensory images and impressions occur in the imagination as the movements of the vapours subdue. Finally, at the end of the sleep, when digestion has completed and when we are sober, we have the clearest dreams. At that time, also one of the other internal senses, the so-called sensus communis, or ‘common sense,’ which combines the input from the different outer senses into one sensory, conscious perception, can become partially unblocked and start to function so that we can become aware of the fact that we are dreaming.27 Yet, the unblocking of the sensus communis is not total and we shall not recognize all dream sensations as only imaginary. At the end of the sleep, even our intellect can begin to be released from the bondage of sleep and can start to function. For example, we can start to reason and syllogise in our dream. However, while still asleep, the freedom of the intellect remains limited and it will not function fully properly. That’s why, upon awakening, we’ll discover that we made errors in our syllogising.28 The lack of freedom of the intellect during sleep also accounts for the a-morality of nocturnal emissions or wet dreams. In sleep, the intellect cannot judge freely and, consequently, we do not have free choice. Therefore, wet dreams are not sins.29 The inner corporeal dream processes can account for some non-coincidental connections between a dream and a future event, in particular future diseases. A certain physiological disposition of a person can lead to corresponding reactions in his or her imagination when dreaming. Aquinas gives several examples, based on the classical medical theory of the humours.30 Someone in whom cold bodily fluids dominate, may dream that he is immersed in water or in snow. When a person dreams she is eating sweets, it signifies that sweet phlegm is prevalent in her body.31 In this way, dreams can tell us something about our health status, which according to ancient medicine depends largely on the right balance between the four humours. Likewise, dreams can also tell us something about latent diseases that have not yet manifested themselves in perceptible symptoms. With reference to Aristotle, Aquinas thinks that such small inner corporeal 26 The ‘imagination’ is somewhat misleading. It does not only gathers visual impressions, but also input from the other senses. When speaking about ‘dream images’, other sensory dream sensations (hearing, feeling, tasting, and smelling) are not excluded. 27 The common sense not only integrates the input from the different sense organs, but also makes that we are aware of sensory perception: In de Anima Sentencia II c. 13 (Opera Omnia, Leonine edition vol. 45.1 [Rome-Paris, 1984] 119-20); S.Th. Ia q. 78 a. 4 ad 2. 28 S.Th. Ia q. 84 a. 8 ad 2; In IV Sent. d. 9 q. 1 a. 4 qc. 1 ad 4 (Scriptum super libros Sententiarum t. 4, ed. M. Moos [Paris, 1947] 387); Sententia Libri Ethicorum 1 lc. 20 (Opera Omnia, Leonine edition vol. 47.1 [Rome, 1969] 71-72). 29 S.Th. IIa-IIae q. 154 a. 5; In IV Sent. d. 9 q. 1 a. 4 qc. 1 (Scriptum t. 4, 386). See also Sententia Libri Ethicorum book I, lc. 20 (Opera Omnia vol. 47.1, 71-72). 30 Connecting dreams with the humours was common: see Kruger, Dreaming in the Middle Ages, 72. 31 S.Th. Ia q. 84 a. 8 ad 2; De Veritate q. 12 a. 3 ad 2 (Opera Omnia vol. 22.2, 377-78). Another example is that seeing a red object in a dream indicates a surplus of blood. This example is in Super Matthaeum c. 27, lc. 1, nr 2336 (Super Matthaeum Lectura, 360); however, the text is not genuine (see note 17 above). 9 movements are better experienced in sleep than in waking, when we are abstracted by so many other, external impressions.32 5. External causes: celestial bodies Besides inner mental and physical causes, dreams can also be brought about by external causes. Just like to internal physiological causes, we are also susceptible to the influence of certain external causes more during sleep than in waking. When awake, our mind is occupied with and focused on the things we perceive around us, and our inner sensory powers are fully engaged by the agitations of the external senses.33 In sleep, these stimuli no longer drown the subtle impressions of some other external agents, and our mind and inner senses become more sensitive to these influences. Again, Aquinas subdivides these external causes into corporeal and spiritual. Likewise, the external cause of dreams is twofold: corporeal and spiritual. It is corporeal insofar as the imagination of the sleeping person is influenced by the surrounding air or from the impression of a celestial body so that certain images appear to the sleeper in conformity with the disposition of the celestial bodies. Corporeal external causes are twofold: they can be nearby, like the air that surrounds the dreamer, or distant celestial bodies. Aristotle mentions only the former explicitly, not the latter.34 Conversely, Aquinas does not examine the proximate external corporeal causes in any of his works, but does explain how the movements of celestial bodies can cause dreams and how they also can be a cause of certain future events.35 He does so in discussing divination through stars.36 The background is the view of Aristotelian and 32 In In II Sent. d. 7 q. 2 a. 2 ad 6 (Scriptum t. 2, 191-192) Aquinas follows Aristotle’s argument in On Divination in Sleep c. 1 463a3-21. Aristotle notes that these medical indications are only conjectural, for it is possible that the disease does not develop: 463b23-32. 33 In II Sent. d. 7 q. 2 a. 2 ad 6 (Scriptum t. 2, 191-192); S.Th. IIa-IIae q. 172 art 1 ad 2; De Veritate q. 12 a. 3 ad 2 (Opera Omnia vol. 22.2, 377); De Veritate q. 28 a. 3 ad 6 (Opera Omnia, Leonine edition vol. 22.3 [Rome, 1976] 829-30 . 34 For Aristotle, see On Divination in Sleep 464a15-18 and On Dreams 460b28-461a4. Aristotle thinks that the celestial bodies exert great influence on the sublunary world (see Meteorology I, c. 2, 339a21-33), but does not mention this in his dream theory. The connection between oneiromancy and astrology within the framework of an Aristotelian natural philosophy was made by Arab thinkers and adopted for example by Albert the Great: Tullio Gregory, ‘I sogni e gli astri’, in idem (ed.), I sogni nel medioevo . Seminario Internazionale Roma, 2-4 ottobre 1983 (Rome, 1985) 111-148. 35 Aristotle points out that minor physical changes around someone who sleeps, can present themselves in a dream, often in magnified form. A faint sound can be experienced as thunder by the dreamer, or a slight raise of the surrounding temperature as walking through fire: On Divination in Sleep 463a11-18. Whether this is a dream-experience in the strict sense for Aristotle, is not clear: cf. Gallop’s note in Aristotle: On Sleep and Dreams, 160. Aquinas nowhere discusses the proximate external causes of dreams. Only in Super Ev. Matth. Lectura, c. 27 lc. 1, nr. 2336 (Super Matthaeum Lectura , 360), the example is given that a cold environment can cause someone to dream he is in snow. However, the text is not genuine (see note 17 above). 36 E.g. in S.Th. IIa-IIae q. 95 a. 5. See also Thomas Litt, Les corps célestes dans l’univers de saint Thomas d’Aquin (Louvain and Paris, 1963), 240-41. 10 medieval cosmology that stars, planets, sun and moon have a strong influence on what happens on earth. They effect the movement of the tides, the change of seasons, and other meteorological phenomena, like rain or specific winds. This sounds familiar to us, but for Aristotle and Aquinas the range of the activity of heavenly bodies extends further and includes e.g. procreation and sensory experiences of animals, including human persons.37 Celestial bodies have no influence on the spiritual human powers like the intellect or the free will, but they can work upon our bodily organs and, hence, upon faculties like the sensory powers, which are connected with specific organs. 38 It is to these subtle cosmic influences that our senses are more sensitive when we are asleep. In conclusion, the same movement of a celestial body can be the beginning of two distinct causal chains, one leading to a dream, the other to a later concrete effect in reality. In this way, dreams can be predictive. But also in this case, the prediction is often a matter of statistical probability and not of absolute necessity. The reason is that the causal efficacy of heavenly bodies on material objects is not always necessary, but can be hindered because of a failing mediating cause or because of a conflicting disposition in the body that undergoes their influence.39 Only necessary natural effects like tides, eclipses and (general) weather conditions can be known with certainty in advance.40 But, of course, for such kind of knowledge we need not depend on dreams. Also other animals can sense in advance specific natural phenomena because of the influence of celestial bodies: birds can anticipate the change of seasons and fish can feel a storm is coming. Animals can do that better than humans and even when they are awake, because they lack reason and therefore their imagination is more at rest, open to cosmic influences, and not so much absorbed by the movements of reason as we are.41 Although Aquinas allows for the possibility of dream divination through celestial bodies, he does not think that it is very reasonable (modicam rationem) to believe in this kind of oneiromancy. It makes more sense to assume not a natural cause like celestial bodies, but a free, intellectual agent, either God and angels or demons. 42 Aquinas does not explain why this is so, but it seems that he thinks that such a natural causation of predictive dreams is statistically rare. 6. External causes: demons, angels and God 37 S.Th. Ia q. 115 a. 3-4, 6 and De Veritate, q. 5 a. 9-10 (Opera Omnia, Leonine edition vol. 22.1 [Rome, 1975]161-71). Sex-determination, for example, is reduced to the influence of heavenly bodies: De Veritate, q. 5 a. 9 ad 9 (Opera Omnia vol. 22.1, 166-67). 38 S.Th. IIa-IIae q. 95 a. 5; De Veritate q. 5 a. 10 (Opera Omnia vol. 22.1, 169-70). In this way, the celestial bodies codetermine the behavior according to natural instinct in animals: S.Th. Ia q. 115 a. 4. 39 De Veritate q. 5 a. 9 ad 1 (Opera Omnia vol. 22.1, 165). 40 See In II Sent. d. 7 q. 2 a. 2 (Scriptum t. 2, 189); S.Th. IIa-IIae q. 95 a. 1. Strictly speaking, such knowledge is not foreknowledge of future effects, but knowledge of present inclinations of causes: De Malo q. 16 a. 7 (Opera Omnia vol. 23, 315). Foreknowledge in a proper sense is an exclusively divine prerogative. 41 In II Sent. d. 7 q. 2 a. 2 ad 6 (Scriptum t. 2, 191-192). 42 Summa contra Gentiles III c. 154 ‘Et licet’- ‘Sed quia’ - hereafter cited as ScG – (Opera Omnia, Leonine edition vol. 14 [Rome, 1926] 451-52). 11 The fourth and final kind of causes of dreams are external spiritual agents. First, Aquinas mentions God and (good) angels. As for the spiritual cause, dreams are sometimes from God, who reveals things to humans through the ministry of angels, as is written in Numbers: ‘Should there be a prophet of the Lord among you, I shall appear to him in a vision, or through a dream I shall speak to him.’ In revealing future events through dreams, angels do not act of their own accord, but as servants or ministers of God.43 God, on the other hand, never discloses future events immediately to prophets, but always uses the mediation of angels.44 In support of this, Aquinas refers to the authority of Pseudo-Dionysius, who applied the Neo-Platonic principle of mediated emanation from the One to the Christian notion of revelation by God.45 Also the traditional theological idea, based on certain passages in the letters of Paul and in Hebrews, that the Old Law was revealed through the angels, in contrast with the direct revelation of the New Law by the God-man Christ, might play a role, as well as the theological consideration that it belongs to God’s goodness to involve creatures in carrying out his providential plan. And there are exegetical arguments in the form of Scriptural passages about angels who appear in a dream as divine messengers (Gen 31:11, Matthew 2:13.19). God has complete, infallible foreknowledge of all future events, including all chance events and free choice actions, even if He is not the direct cause of them, as in the case of evil as such and of sin. All that happened, happens and will happen in time is present to him and can therefore be known by him because of his unique, ineffable mode of being, viz. timeless eternity.46 He can let people share in his foreknowledge, who then become prophets. One form of prophecy is by sending dreams.47 Although prophecy is a supernatural kind of knowledge, it involves the ordinary human cognitive powers. Only in this way, it can be truly human knowledge. According to an Aristotelian epistemology, human beings cannot come to know something unless through their sensory faculties, both the outer and inner senses. As our mind and senses are less distracted by the everyday things of life when we are asleep, God can affect human imagination more naturally and effectively through dreams. More details about the epistemic process in God-sent, revelatory dreams, and about the mediating role of 43 Cf. ScG III c. 154 ‘Sed quia’ (Opera Omnia vol. 14, 452); De Veritate q. 12 a. 3 (Opera Omnia vol. 22.2, 376). 44 Cf. S.Th. IIa-IIae q. 172 a. 2; De Veritate q. 12 a. 8 (Opera Omnia vol. 22.2, 394); Super Isaiam c. 6 (Opera Omnia, Leonine edition vol. 28 [Rome, 1974] 48-49). 45 S.Th. IIa-IIae q. 172 a. 2; Super Isaiam c. 6 (Opera Omnia vol. 28, 48). The reference is to On the Celestial Hierarchy 4 (Migne, PG 3, 180C), Pseudo-Dionysius, The Complete Works, transl. by Colm Luibheid (London, 1987), 157. Also in Calcidius’ influential Neo-Platonic Commentary on Plato’s Timaeus, it is said that divine revelation is always mediated by ‘divine powers’ (divinae potestates), see Kruger, Dreaming in the Middle Ages, 29. 46 See S.Th. Ia q. 13 a. 8-13. 47 Cf. note 14 above. 12 angels in them will become clear when we look at the possible role demons can play in dreaming. Not only God and good angels, also fallen angels, demons, can produce images in persons who are asleep. Sometimes, however, it is through the activity of demons that certain images appear to persons who are asleep, by which they [=demons] reveal some future events to those with whom they made an unlawful pact. Demons can have some knowledge of future events. However, their foreknowledge differs fundamentally from God’s because they are not timelessly eternal. They cannot know future events as these exist in themselves, but only insofar these are now latently present in their causes, and therefore it is not foreknowledge in the strict sense.48 Although their knowledge of what is going to happen, does not extend as far as God’s, their natural intellectual powers far surpass that of humans so that they can foretell future effects, insofar as these are virtually contained in present causal tendencies, much better than we.49 For example, humans can predict a thunderstorm coming when they see dark clouds and feel the air is humid. The knowledge demons have of the nature of things, of how they work, and of how they interfere with each other, exceeds ours greatly. Moreover, it is not limited to physical, but also includes psychological phenomena. Angels have better knowledge of a person’s character and, hence, more information about how he or she will probably act. In sum, angels have much more detailed knowledge about future effects, even though also this knowledge remains largely conjectural. 50 Only of events that necessarily follow from present causal tendencies, demons can have certain foreknowledge, e.g. of future solar eclipses. Of all other events, they can more accurately estimate what the chance is that they will occur, but such events are not completely causally determined and the possibility remains that they do not happen. Aquinas thinks that there are genuine chance events in nature and also that humans have free choice.51 How can demons inform us about their prognostications about the future? They cannot imprint their knowledge directly upon humans because their mode of knowledge differs fundamentally from ours. Being purely spiritual, they have a purely spiritual mode of knowing. The same goes for the good angels.52 If a demon or a good angel wants to transfer to us what it knows, it has to adapt the communication process to our human way of knowing and of learning. Although humans, insofar as they are 48 Cf. note 40 above. 49 De Veritate, q. 8 a. 12 (Opera Omnia vol. 22.2, 259). 50 Contrary to modern usage, Aquinas does not call demonic or angelic knowledge and activity ‘supernatural’. As creatures, also purely spiritual agents have their own natural capacities. 51 See S.Th. Ia q. 57 a. 3; In II Sent. d. 7 q.2 a. 2 (Scriptum t. 2, 189). 52 Among themselves, angels (and demons) communicate by a kind of telepathy. See S.Th. Ia q. 106-107. 13 spiritual beings, have the capacity for intellectual knowledge in contrast with animals that only have sensory knowledge, our intellect can only function properly when it works in unison with our sensory faculties. Therefore, demons and good angels need to operate on our bodily sensory faculties if they want to communicate with us. Sleep gives them a good opportunity to affect our inner and outer senses. Because corporeal substances obey naturally a spiritual agent when the latter moves them with regard to place, demons and angels can interfere with the natural process of dreaming by stirring the bodily vapours and humours that produce dreams, as we saw above. More specifically, this manipulation can have two effects.53 The first one is that sensory images stored in the inner sense of the imagination flow to the organs of the outer senses, so that it actually feels as if the things imagined are really present. The second is that the outer senses are changed, like when someone whose taste has been harmed, experiences all food as bitter. Demons can bring about such bodily changes either directly or indirectly, by means of certain substances as instruments. Aquinas gives an example of the latter: ‘Just like when upon the evaporation of a certain smoke, the beams of the house seem to be serpents, and one finds many more of such experiences.’54 Aquinas concludes the discussion in Summa Theologiae IIa-IIae question 95, article 6 as follows: Therefore, it must be said that if someone uses dreams in order to foreknow the future, in as much these come from divine revelation, or from a natural cause, either internal or external, as far as the power of such a cause can reach, it will not be unlawful divination. If, however, such divination is caused from a revelation of demons, with whom a pact has been made expressly, because they are invoked for this, or tacitly, because such divination extends to what it cannot extend, then it will be unlawful and superstitious divination. With regard to the second half of the conclusion, where mention is made of a tacit pact with demons, it is not immediately clear whether Aquinas thinks that demons can effect the sensory changes in our sleep without our prior free and conscious consent. On the one hand, as we saw above, it belongs to the demons’ natural powers to influence corporeal substances, including fluids and gasses in the human body. Furthermore, in a text from the Commentary on the Sentences, Aquinas states that ‘astrologists mostly foretell true things about the future […] on the basis of an hidden instigation of a demon, 53 In II Sent. d. 8 q. 1 a. 5 ad 4 (Scriptum t. 2, 215-16); De Malo q. 3 a. 4 (Opera Omnia vol. 23, 76); S.Th. Ia q. 111 a. 3 and 4; S.Th. Ia-IIae q. 80 a. 2. In some texts, Aquinas speaks of ‘bodily spirits’ (corporales spiritus), but this expression seems to be synonymous with ‘vapours’: see In I Sent. d. 10 q. 1 a. 4 (Scriptum super libros Sententiarum t. 1, ed. P. Mandonnet [Paris, 1929] 267-68). 54 In II Sent. d. 8 q. 1 a. 5 ad 4 (Scriptum t. 2, 215-16). I do not think Aquinas is speaking out of personal experience here. As far as I know, none of the biographies and hagiographies of Thomas Aquinas mention that he ever experimented with psychedelic substances. 14 which human minds sometimes unknowingly (nescientes) undergo; and in this way, one somehow enters into a covenant (foedus) with such kind of divinations.’ Apparently we can unwittingly be subject to demonic influences in our dreams. On the other hand, talking about a ‘covenant’ (foedus) suggests an agreement by two parties and, hence, some kind of voluntary and conscious assent by the human partner. The same goes for the term ‘pact’ (pactum). In Summa Theologiae IIa-IIae question 95, article 6, Aquinas speaks about having an explicit or a tacit pact with demons in the case of divination through dreams.55 An explicit pact, Aquinas says, is made when demons are actually invoked in so many words. On the other hand, there is an implicit pact ‘when the divination extends to what it cannot extend.’ Also qualifying oneiromancy through demons as unlawful and as a form of the sin of superstition presupposes a free act of consent by the human person. After all, as we saw earlier, in discussions about nocturnal pollutions, Aquinas denies that they are sinful, because in sleep we do not have free intellectual and moral judgment. When asleep, our senses are bound, from which human knowledge originates and without which our intellect cannot properly function.56 A solution for this apparent contradiction can be found when we take into account that dreams, which belong to the domain of the senses, must be interpreted, which is an act of the human intellect. 7. Interpretation of dreams In the text of S.Th. IIa-IIae, q. 95 art. 6, nothing is said explicitly about the criteria for interpreting dreams or about who has the authority to do so. However, the meaning of dreams is not evident and dream images are often distorted. Belonging to the realm of the sensory power of imagination, dreams need the judgment of the intellect in order to become meaningful. The condition and the level of the intellect – and not the dream images themselves – are decisive for gaining knowledge from dreams. In the Summa contra Gentiles, Aquinas says: From whatever imaginary forms, a person cannot gain any intellectual knowledge beyond the natural or acquired capacity of one’s intellect. That is also obvious in dreams, in which – even if there is some prefiguration of future events – not everyone who sees the dreams, understands their meaning.57 By nature, the intellectual judgment on the meaning of dreams works far better awake than asleep. We understand and interpret dreams best later, when awake. 58 Moreover, 55 Likewise in S.Th. IIa-IIae q. 92 a. 2 co. and ad 2. This does not fully agree with the division of kinds of divination in S.Th. IIa-IIae q. 95 a. 3, where divination through dreams is classified as a form of divination by means of express invocation of demons 56 See note 29 above. 57 ScG III c. 104 ‘Deinde’ (Opera Omnia vol. 14, 325). 58 De Veritate q. 12 a. 3 ad 1 (Opera Omnia vol. 22.2, 377) and a. 13 (Opera Omnia vol. 22.2, 411); S.Th. IIa-IIae q. 172 a. 1 ad 2. See also note 23 above. 15 in the case of truly prophetic, God-given dreams, the natural capacity of our intellect does not suffice. These dreams reveal genuine future coincidences and free actions of rational beings, which are not already predetermined in present causal tendencies and for which there is no natural causal explanation yet. Therefore, through the good angels, God does not only send the sensory dream images, but also an additional, supernatural enlightenment of our intellect for interpreting the images. Without this ‘prophetic light’, one is not a prophet. Strictly speaking, the dream images by themselves do not yet count as prophecy. The true prophet is not the one who has dreams, but the one who knows how to interpret them.59 Therefore, Pharaoh and king Nebuchadnezzar, who had dreams sent by God, but not the supernatural enlightenment to understand them, were not truly prophets, while Joseph, when he interpreted not his own dreams, but those of Pharaoh, was a prophet in the full sense of the word. The intellectual enlightenment only goes for God-sent dreams. In his early work, Aquinas suggests that besides corporeally modifying our internal and/or external senses, demons can also influence our knowledge spiritually, viz. by strengthening the natural light of the human intellect.60 However, in later works, he states that although it is within the natural capacity of demons to enlighten our mind, in reality they never do so because that would thwart their intention to deceive us. Only good angels actually enlighten us.61 Therefore, in the case of dreams caused by demons, the interpretation is a matter only of the natural capacity of our intellect. This can help us to understand the text in S.Th. IIa-IIae, q. 95 art. 6, where Aquinas writes about dream diviners who have a ‘pact tacitly made [with demons] because such divination extends to what it cannot extend.’ In my view, what he means by ‘tacit pact’, is divination as an act of the human intellect in its natural state, without supernatural enlightenment. Divination concerns primarily the interpretative act of the human intellect, not the more of less passive reception of dream images, caused by demonic activity. That act of the intellect is a conscious, voluntary human act, and hence, can be the object of a moral judgment, unlike the dream itself. Choosing to interpret a dream sent by demons as predicting some future event can then be seen as a form of cooperating with demons and of entering into a ‘tacit pact’ with them. Such an act is immoral and against the divine law. However, there is yet another problem with this text. The pact is said to be tacit ‘because such divination extends to what it cannot extend.’ This seems to suggest that one cannot know future events by way of divination through demonic dreams. But the opposite is true. Divination through demonic dreams can yield genuine knowledge about a future event or at least about its statistical probability. Although we should not do it and although we often fail through incorrect interpretation, we can still learn something about the future from demonic dreams. After all, although demons do not 59S.Th. IIa-IIae q. 173 a. 2; De Veritate q. 12 a. 10 ad 14 (Opera Omnia vol. 22.2, 402); Super I Epistolam ad Corinthios Lectura c. 14 lc. 1 nr 812 (Super Epistolas S. Pauli lectura t. 1, ed. R. Cai [Turin and Rome, 81953] 390). 60 In II Sent. d. 7 q. 2 a. 2 (Scriptum t. 2, 190). 61 De Malo, q. 3 a. 4 (Opera Omnia, vol. 23, 75); ScG III c. 154 ‘Ea vero’ (Opera Omnia vol. 14, 451); S.Th. Ia-IIae q. 80 a. 2. 16 have God’s absolutely infallible foreknowledge of future contingencies, they know the present inclinations of causes far better than we do and can forecast with much more accuracy their probable outcome. Therefore, when Aquinas says that ‘such divination extends to what it cannot extend,’ he cannot mean that such divination is impossible, on pain of contradiction. It seems rather an elliptical way of saying that when we try to foretell the future through demonic dreams, our intellect goes beyond what it is capable of by nature, and without the special divine assistance. It aims at knowledge that it cannot acquire from natural data, viz. the physiological input from one’s own body and the cosmological input from the heavenly bodies, but for which it depends on the activity of voluntary, spiritual agents, viz. demons. How can we know what the origin is of a predictive dream? What criteria do we have for deciding whether there is a natural explanation and, if not, whether the dream is sent by God or by demons? And who has the authority to interpret dreams? Aquinas himself does not address these questions explicitly, but we can reconstruct what he might have answered. First, scientists like medical doctors and cosmologists can show that a predictive dream has a natural, corporeal cause, either internal or external. Such predictions had better not be called ‘divination’ or ‘prophecy’, but ‘skill’ (ars).62 Second, if there is no such natural explanation, the question arises if the dream is from God or from demons. Inner emotional perceptions can be indicative of the dream’s origin. The unfamiliarity of dreams that come from higher spiritual agents, causes fear in the dreamer. When the dream comes from a good angel, the fear will turn into consolation, but when it is from a demon, the dreamer will remain in terror. 63 Furthermore, one might expect that a person also feels or is conscious of the gift of the supernatural illumination of the intellect. Consequently, awareness of the lack of the prophetic light points to a demonic origin. Next, also the content of the prediction can be a sign. If it does not concern human salvation, it is not a God-sent prophecy. All prophecy is about what is useful or necessary ‘for instruction in the faith or for formation of morals.’64 Therefore, predictions that are not for the purpose of human spiritual welfare, but are about futile events, financial self-interest and the like, do not come from God. Finally, the moral or intellectual excellence of the dreamer gives no evidence about the origin of the dream. Aquinas turns Aristotle’s argument that dreams cannot be divinely inspired because they happen to ‘persons of inferior type’ around. The very fact that any type of person can have prophetic dreams, shows that such 62 De Veritate q. 12 a. 3 (Opera Omnia vol. 22.2, 376). Aristotle also speaks about ‘distinguished physicians’ in this context. See Philip J. van der Eijk, ‘Aristotle on “distinguished physicians” and on the medical significance of dreams,’ Clio Medica 28 (1995) 447-459. 63 Expositio super Iob c. 4 (Opera Omnia vol. 26, 31).; Super Ev. Matth. Lectura c. 1 lc. 4, nr. 128 (Super Ev. Matth. Lectura, 19). Super Ev. Matth. Lectura c. 27 lc. 1, nr. 2336, it is said that it is not clear whether the dream of Pilate’s wife is from God or from the devil. However, this text is not genuine: see note 17 above. 64 De Veritate q. 12 a. 2 (Opera Omnia vol. 22.2, 371). 17 dreams are purely a matter of grace and not of some inherent excellence of the dreamer. It depends solely on God’s election.65 As of astrological divination, Aquinas is in the end rather pessimistic about the statistical probability of a God-sent dream. Most of times (plerumque), there is a demonic and not a divine/angelic origin.66 8. Conclusion Aquinas tries to harmonize Aristotle’s natural explanation how dreams can signify a future event with biblical accounts about divine prophecy through dreams. The theological meaning of the biblical texts does not necessarily imply a magical worldview, but can go together with the conception of a well-ordered cosmos, where things have their proper activities and produce their own effects, which can be scientifically examined by human reason. More in particular, Aquinas sees the human person as a unity, an animated body or an embodied soul, in which corporeal senses and the spiritual intellect have to work in unison if there be a genuinely human cognitive act. This condition also applies to predictive dreams. Aquinas distinguishes three kinds of predictive dreams: (1) natural forecast, (2) divination, (3) prophecy. First, certain subtle physiological processes within the human body and also external cosmological influences are better perceived in sleep than awake and can cause specific dream images. Skilled experts like physicians and natural philosophers can infer from these symptoms present inclinations and predict with some degree of probability medical or meteorological developments. Second, divination happens through demonic activity. Demons do not have foreknowledge of the future as it exists in itself, but they have insight into the present tendencies and processes of nature and of psychological characters, much more even than human scientists. By influencing our senses when we are asleep, demons can let us share in their conjectural knowledge about the future. We are not morally responsible for the dream images that they cause in our senses, but when we consciously try to interpret such images by means of our intellect, we commit the sin of divination. Third, a dream is prophetic when sent by God through the mediation of good angels. God has complete, absolutely certain foreknowledge of the whole future, including all contingent events, and can impart some of it to us with the intention to promote our salvation. He involves angels in the sending of prophetic dreams. Like demons, also good angels can affect our senses during sleep and stimulate certain sensory images, but unlike demons, the good angels also strengthen our intellect with the gift of the prophetic light. Although Aquinas acknowledges that dreams can be predictive of future events, he remains very cautious about using and trusting them. Naturally caused dreams need the interpretation by scientific experts and occur less frequently than dreams caused by demons. Trying to interpret the latter is a sin. Moreover, the predictions in natural and 65 De Veritate q. 12 a. 5 ad 4 (Opera Omnia vol. 22.2, 384). See also S.Th. IIa-IIae q. 172 art 4 ad 4. In II Sent. d. 15 q. 1 a. 3 ad 4 (Scriptum t. 2, 377); ScG III c.154 ‘Et licet’- ‘Sed quia’ (Opera 66 Omnia vol. 14, 451-52). See note 42 above. 18 demonic dreams about contingent future events are not absolutely certain, but only probable to some degree. Finally, truly divinely inspired prophetic dreams are possible, but they are an inferior kind of prophecy compared to e.g. daytime ‘visions’ and they are very rare. Not private revelations, but God’s public revelation in Scripture, in nature, and above all, his final self-disclosure in Christ and in the Spirit, are the guiding principles in faith. However, Aquinas’ reticence about predictive dreams does not mean that they play no role in his theology, as Kelsey concluded.67 Aquinas develops a dream theory within a comprehensive Christian worldview in which all creatures, both physical and purely spiritual substances, have their own activity and causal effects under God’s providence, and in which the human person, being a corporeal-spiritual unity, needs both the physical senses and the spiritual intellect in order to produce any cognitive act whatsoever, including all acts of supernatural and prophetic knowledge. 67 See note 9 above. 19