The Soul between Body and Immortality: The 13th Century Debate on the Definition of the Human Rational Soul as Form and Substance

Evelina Miteva (Bari – Cologne)

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If we consider the soul in itself, then we agree with Plato;

 but if we consider it according to the form which it gives to the body and animates it, then we agree with Aristotle.[1]


The nature and the origin of the human rational soul have always provoked a particular philosophical interest. Its problematic character arises by its natural connection to the body on the one side, and by its apparently non-bodily related capacities as thinking or moral acting. This tension between corporeal and incorporeal realm within the soul found two basic solutions in ancient and medieval philosophy, the Platonic one that regarded the soul as an independent and immortal substance, and the Aristotelian one, according to which the soul is intrinsically bound to the body.

  1. Medieval Background

In the early Middle Ages, the understanding of the soul-body relation was shaped by Augustine’s definition of the soul as a governor of the body. In the well-known passage from De quantitate animae he says:

But if you want to define the mind for yourself, and so ask what the mind is, it is easy for me to reply. For it seems to be to be a certain substance, partaking in reason, and fitted to ruling the body.[2]

This statement put the soul in the gender of the substances, making it separate and independent from the body reality. Yet, a dualism that separates the soul from the body would be contrary to the Christian spirit and would imply the possibility for heretical conclusions, such as that of the Manicheans, where the body has a negative moral value. Augustine seems to have been struggling from the earliest to the last of his writings after his conversion over the nature of that union between immortal soul and mortal body.[3] But although he never establishes a consistent theory of the soul-body relation, he is clear in his understanding about the soul as an immortal substance, which is nevertheless created with relation to a certain living body.

Augustine’s views on the nature and dignity of the soul, which is able to ascend to the supreme good in a moral and ontological respect, draw strongly on Neoplatonic philosophy, flourishing at that time (it is worth reminding that one of the most prominent Neo-Platonists, Proclus, was not yet born in Augustine’s time). And by an irony of the historical fate of philosophy, it was another Neoplatonic influenced group of authors that shaped the understanding of the soul in the 8th century. As the Arabs slowly were conquering Christian and Hellenic territories, they were also acquiring Greek knowledge. Since Al-Kindi (ca. 801-873), many of Aristotle’s works, together with later Peripatetic commentators and Neoplatonic authors, were read and discussed in the Arab world. And many of the Arab writings were in their turn translated into Latin, providing the Western world new insights into the understanding of the body-soul relation. And it was probably because of their familiarity with the Early-Christian Neoplatonism of Augustine, Boethius and Pseudo-Dionysius the Areopagite that those ideas were so influential for the Latin High Middle Ages.

Avicenna (ca. 980-1037) was the one who came out of the Platonic-Aristotelian dichotomy with a new solution. Plato defines the soul as a self-moving thing, and whatever moves itself is immortal.[4] This independence of the soul is opposed by the Aristotelian view of the soul as the form of a living body.[5] A consequence of the Aristotelian view is that the soul perishes with the dissolution of the body. But Avicenna claimed that those two views are not necessarily contradictory. He claims that they are two different aspects in the soul’s nature. The Aristotelian approach is nevertheless subordinated to the general Neoplatonic scheme. We can admit, says Avicenna, that the soul is a form of the body, if we only keep in mind that this is its main function, but not its essence. By its essence the soul is a spiritual substance, independent from the body. Its self-sufficiency is confirmed by the argument that it can be known without any reference to its bodily existence[6], very much in the same way as we can read a book and make certain assumptions about its author without having sensitive data about the actual person. The spiritual character of the soul is confirmed, moreover, by its ontological status. In a Neoplatonically shaped description of the world, the soul, according to Avicenna, is the lowest of the separate substances, belonging in this sense to the intellectual world; but because of its ontological weakness it requires a body to carry out its actions.[7] This means that the soul needs the body as its instrument, and therefore does not relate to it in an essential way. The soul (anima) animates the body, but this is only one of its functions, what is more, an accidental one. Significantly, Avicenna says:

This name, “soul”, is not attributed to it on behalf of its substance, but because it rules the bodies and is assigned to them, and respectively receives the body in its definition, for example as the work is accepted in the definition of the workman, even if it is not accepted in his definition as a human being.[8]

The operation of the soul does not relate to its definition, nor does the body relate to the definition of man. In accordance with his theory, Avicenna systematically preferred the term perfectio, rendering the Greek entelecheia, rather than form, since the latter is a notion clearly opposite to the notion of substantia.[9]

So if taken into its relation to the body, the most adequate definition of the soul is perfection.

  1. Paris, 8th century

Avicenna’s attempt to reconcile those two notions, substance and form, that look contradictory and yet equally necessary for defining the soul’s nature, proved to be influential in the Latin XIIIth century. The most prominent university of that time, the one in Paris, hosted in a very short span of time three of the most renowned masters of theology: Albert the Great (1200 – 1280) occupied the chair of theology of the Dominican order in the Paris university from 1245 to 1248, where his pupil was Thomas Aquinas (1225 – 1274); later on, Thomas held the same chair from 1256 to 1259, and once again from 1269 to 1272; and their counterpart, Bonaventure (1217 – 1274) occupied the Franciscan chair in the Faculty of Theology in Paris from 1254 to 1257. All three of them took a position on the tricky form-substance dilemma.

Albert the Great

According to all evidence[10], Albert draws on Avicenna in distinguishing the essence from the function of the soul. Yet, he does not seem to be unaware of the inner tensions of this theory. The most obvious one is that the “substantialist” position holds for the incorporeal and independent character of the soul, while the “hylomorphic” view sustains that the soul is one of the qualities of the whole substance, i.e. the human being as such. Moreover, the soul cannot be a form and at the same time a substance, because the substance is already something composed of matter and form. Hence, claiming that the soul is in a certain respect a form and in another a substance would imply necessarily that there is more than one form in the soul, a view that became historically known as plurality of forms. Another consequence would bind the supporter of such a position to the postulating of some spiritual matter in order to preserve its substantial status. Both ideas were actually held by Ibn Gabirol (ca. 1021/2 – 1057/8), the author of the philosophical work Fons vitae (The Fountain of Life), influential in the Latin world.

Albert the Great criticizes those views[11], which is a clear sign that he is conscious of the complexity of the problem and does not simply adopt a conciliatory position. Nonetheless, there are claims in modern secondary literature that Albert’s position was “eclectic”[12] and his view on the soul and its cognitive power was a “facile reconciliation” of Plato and Aristotle[13]. Such a strong statement surely needs some evidence, and Albert indeed provides one. He seems for example to have overlooked an important argument from the early patristic work The Nature of Man (ca. 400, attributed in the Middle Ages to St. Gregory of Nissa and actually written by his contemporary Nemesius of Emesa), one of the sources to which Albert often refers. This work, strongly influenced by Neoplatonic philosophy, rightly pointed out that something that is a form of a body cannot be an incorporeal substance.

At this point of the problem Albert adopts the Avicennian distinction between essence and function of the soul. This position is, however, vitiated as dualist. That is why Albert seeks for further distinctions to clarify his view. Albert takes as given that the soul has to be in some way independent from the body, because, from a theological point of view, this is a prerequisite for the immortality of the soul, and, from a philosophical standpoint, it is a plausible explanation for the universality of knowledge. This means that he has to explain in what way the soul is a substance. A substance traditionally is defined as a matter-form composite. Albert systematically avoids this division, and substitutes it for the Boethian quo est – quod est division, i.e. the soul consists of that through which it is and that which it is.[14] In the structure of the rational soul these principles correspond to the active and the possible intellect (intellectus activus – intellectus possibilis). That is how the soul subsists and is individual without being material. But it is at the same time naturally bound to the body, for it is its perfection. Similarly to Avicenna, Albert prefers the term “perfection” to “form”. The soul comes into existence in the individual body, and it is intrinsically bound to its functions.[15] The soul is the perfection of the body as the sailor is the “perfection” of his ship[16], the one falls into the definitions of the other. But this is still a functional explanation.

That is why here we will focus on another distinction, the threefold distinction in the functions of the soul – animation, intellection, and divine function.[17] The first two functions of the soul, the animation of the body and intellection, are discussed also by Aristotle and they fit well with the definition of the soul as form. The third operation is the divine one – this means that the soul transcends the body, as God transcends the world, and it means also that it is able to do the divine work (opus divinus), i.e. to contemplate and know the separate beings.[18] But the divine operation, which in other Albertinian works is explained in the terms of formal conjunction between the possible and the active human intellect, transcends the Aristotelian background. I believe that maybe here one could search for the solution to the tension between the soul-form and soul-substance definitions.

By its essence the soul has bodily-related functions, and a divine function that transcends the body not only on a logical level (where Albert places intellection), but also on a metaphysical level – the intellect is separable, and yet the essence of man. The soul is able to perform all three operations, the natural, the intellectual and the divine, because it is an image of God. All the complex views on the nature of the human soul that Albert holds are sustained by this theological foundation.

What is more, the divine essence of the soul, i.e. its immortality and spirituality, is described side by side with animation and intellection as a function of the soul. This is to say, the Avicennian subordinating model is surpassed by making the function a part of the essence, and by endowing the soul with a bodily-independent function, the divine one.

Thomas Aquinas

In his early writings Thomas shared many of the points of his teacher[19], trying, as it seems, to find his own way out of the doubts that both Aristotle and Avicenna left in their accounts on the soul. But by 1267-68 with the Quaestiones disputatae de anima (Questions on the Soul) he had developed a different approach, which became known for its coherence and simplicity.

Much like for his distant predecessor Nemesius, it was unconceivable also for Thomas that something could be both form and substance. But unlike Nemesius, Thomas had at hand the detailed arguments and theories on the soul that were developed during the intervening centuries. For this reason, in Question 1 he formulates the problem in a very precise way: Utrum anima possit esse forma et hoc aliquid (“Whether the soul can be [both] form and individual thing”). Crucial here is the notion of hoc aliquid that literally translates the Aristotelian tode ti. For Aristotle it stands first of all for the individual matter-form being, and only in a derivative and secondary sense it means the form through which the individual is that which it is. So for Thomas the problem was not if the soul can be called form and in some way also a substance, but if it could be form and at the same time a substance in its proper sense, as something subsisting and individual, i.e. a hoc aliquid.[20]

Aquinas investigates if the soul could be called a hoc aliquid in the proper sense, i.e. if it meets the requirements to exist independently (to subsist), and to be a complete substance in its own right (to be an individual). The rational soul meets the first feature, it is independent from matter not only because it is hierarchically worthier[21], but also because it does not require a bodily organ for its most proper function, intellection. Despite the fact that the rational soul knows in an abstractive way, i.e. takes material from the sensitive data, it is able to surpass the sensitive level and to form universal ratiocinations.[22]

Aquinas, however, defines the soul first of all as a substantial form, because it is the principle of being (esse) for living things. The opposite is reduced to absurd; the principle of an essence cannot be its form only by accidence. The same argument holds true also in the specific case of the human rational soul. It has to be a substantial form, because otherwise the person would be only an accidental composite. This definition leads to the conclusion that the soul, as a substantial form, is ontologically related to the body and hence cannot stand the requirement of being a complete and individual substance.[23]

In this way Aquinas gave a clear and final response to the questions that piled up in the works of his predecessors.[24] The soul is a form in a genuinely Aristotelian sense, not a substance, and thus it is essentially bound to the body. He maintains nevertheless, and by doing so deviates from orthodox Aristotelianism, that the soul preserves some independence in respect to the body, apparent by its capacity of intellection. In Thomas’ account of the nature of the soul there is, however, not only philosophical clarity, but also a theological depth. The immortality of the soul is exemplified by its intellection, but it is fulfilled precisely by its substantial incompleteness. The bond of the rational soul to its body is preserved and gives a rational explanation for their reunion in the time after the Last Judgment.[25] In this way the definition of the soul only as a form does not bear a risk, but affords an opportunity – the opportunity to understand the strange incomplete status of the soul in this world, and at the same time its fulfillment in the resurrection.


Most modern scholars regard Thomas Aquinas’ philosophical accomplishment as a philosophical breakthrough. If we adopt this point of view, then the position of Bonaventure, teaching in Paris in the very same years as Thomas, starts to seem peculiar. Bonaventure was surely acquainted with the problem at stake, with the solutions and the arguments provided by the previous authors and even by Thomas himself. Yet, he chose to defend an apparently old-fashioned position, and here I will try to briefly sketch a possible explanation why, by examining once again the form-substance problem in respect to the human rational soul.

Despite holding on to the Augustinian tradition, Bonaventure recognizes the sense of the Aristotelian definition of the soul as a form of the body.[26] It gives the form of life, motion, and intellection to the body. But the soul is not inseparably bound to it, as Aristotle suggests. It is independent of the body (even if we regard only the cognition) and immortal, and these points suggest that the soul should be defined also as a substance. Here again we have Aristotle or his Peripatetic commentators speaking: a substance is a matter-form composite. That is how Bonaventure comes to postulate a hylomorphic structure also for the soul, consisting respectively of spiritual form and spiritual matter.[27]Albert respectfully, but openly, opposes this theory[28], since for him the introduction of matter in the soul seems inconvenient for many reasons. Both admit, though, that there are possible and active parts of the soul that constitute the substantiality of the soul, but give them different names which bear different implications. The goal of Bonaventure is to parallel the body and the soul as both consisting of matter and form. In this way he could at the same time claim the substantiality of the soul (it is a hoc aliquid) and its intrinsic relation between body and soul. Being structured in the same way, they have a natural inclination towards each other so that they perfect one another.[29]

These short notes on his theory could, however, suggest two basic observations. First, Bonaventure, as it seems, was not as old-fashioned as his “Augustinian” fame suggested. He was well aware of the debates and the philosophical language of his era and was making use of them in his own theories. Second, what we, from our historical perspective, tend to regard as the philosophical mainstream, was actually one of the well-grounded rivals. The opposition between Thomas Aquinas and Bonaventure, the most prominent Dominican and Franciscan scholars, seems, nevertheless, determined. Not only did they occupy the chairs of theology for their orders in Paris in the same period, but they were even declared Doctors of the Church almost simultaneously. In 1482 the Franciscan Pope Sixtus IV bestowed this honor upon Bonaventure, and not long afterwards in 1567 the Dominican Pope Pius V did the same for Thomas.


The majority of scholars working on Scholasticism focus on the differences between the authors and on the innovative character of Thomas Aquinas’ solutions. The most eminent difference, as far as our topic is concerned, is that while Avicenna, Albert the Great, and Bonaventure – to name the main figures in the debate, but actually there were also many other masters of the faculties of arts and theology – held some version of the “eclectic” principle that the soul is a form and substance, Thomas made the radical step of reducing the soul to form. But the brilliance of his solution was that by doing so he also found a way to take account of the soul’s immortality, which was the main reason for the Christian authors since Augustine to define the soul first of all as a substance. I would, however, rather focus on the points of convergence between the authors. The most obvious one is the predominant theological concern. And if this is one of the distinctive features of Bonaventure’s philosophy[30], it is less obvious in Albert the Great and Thomas Aquinas’ works that are focused on commenting upon Aristotle and natural philosophy.[31] But their philosophical enterprise is grounded on a theological impulse and their solutions reflect, in a different way, the ultimate theological goal of their work. Albert focuses on the divine function of the soul and its ability to contemplate the divine essences in this life. Thomas believes that this fulfillment of human nature can be achieved only in the afterlife.[32] Both, however, see the perfection of the rational soul as transcendentally grounded. And probably the problem of the soul as form of the body and at the same time an immortal substance could not be solved in a consistent philosophical manner. Because, by its nature, the soul is “stretched” between the realms of the corporeal and of the spiritual, and this tension is what makes it human.[33] Et ideo etiam in ea parte qua homo mundo nectitur, non mundo subicitur, sed praeponitur ut gubernator.” Cf. T. W. KÖHLER, DE QUOLIBET MODO HOMINIS. Alberts des Großen philosophischer Blick auf den Menschen (= Lectio Albertina 10),

Evelina Miteva (Vilnius, Lithuania, 1981) holds a PhD in Medieval Philosophy from the University of Sofia. She has specialized in the Albertus-Magnus-Institut (Bonn, 2004), in the Thomas-Institut (Cologne, 2007/08) as a DAAD-scholarship holder, and in the Catholic University of America (Washington D.C. 2011/12). Currently she is working on her dissertation in the field of Medieval Philosophy within a bilateral program between the universities of Bari (Italy) and Cologne (Germany).

Author of articles, book- and article reviews, translations into Bulgarian from Latin, German and English.

Research Interests – Medieval Philosophy, Ancient Philosophy, Ethics; Albert the Great, Aristotle, Averroes.

[1] ALBERTUS MAGNUS, Summa theol. II, tr.12 q.69 m.2 art.2, Ed. Borgnet t.33, p.16b: “Ad aliud dicendum, quod animam considerando secundum se, consentiemus Platoni: considerando autem eam secundum formam animationis quam dat corpori, consentiemus Aristoteli.” The English translation is mine.

[2] AUGUSTINUS, De quantitate animae, 13, 22 (PL 32, 1048): “Si autem deffiniri tibi animum vis, et ideo quaeris quid sit animum; facile respondeo. Nam mihi videtur esse substantia quaedam rationis particeps, regendo corpori accomodata.” English translation according to ST. AUGUSTINE, The works of Saint Augustine: a Translation for the 21st century, E. HILL (translation and notes), J. E. ROTELLE (ed.), New City Press: Brooklyn, N.Y. 1990.

[3] Cf. AUGUSTINUS, De beata vita 1, 5 (PL 32, 962); Retractiones 1,1; 2,45. 71 (PL 32, 583. 649).

[4] PLATO, Nomoi 896 a 1-2; Phaedrus 245 c.

[5] ARISTOTELES, De anima, 412 a 21, English translation by W. S. HETT, Aristotle. On the Soul, Parva Naturalia, On Breath (The Loeb Classical Library), London-Cambridge, William Heinemann Ltd.-Harvard University Press, 1957, p. 69.

[6] AVICENNA, Liber de anima seu sextus de naturalibus, V, 1, in S. VAN RIET (Ed.), Avicenna Latinus, Louvan-Leiden, Ed. Orientalistes-E. J. Brill, 1968, p.36, 54-37,68.

[7] Ibid., V, 3, 104, 22-24; 105, 40-44.

[8] Ibid., I, 1, p. 26, 27-27,32: “Hoc enim nomen anima non est indutum ei ex sua substantia, sed ex hoc quod regit corpora et refertur ad illa, et idcirco recipitur corpus in sui definition, exempli gratia, sicut opus accipitur in definition opificis, quamvis non accipitur in definition eius secundum quod est homo.” The English translation is mine.

[9] Cf. B. CARLOS BAZÁN, “The Human Soul: Form AND Substance? Thomas Aquinas’ Critique of Eclectic Aristotelianism”, in AHDLMA 64 (1997), p.95-126, in part. 103-104; É. GILSON, “L’âme raisonnable chez Albert le Grand”, in AHDLMA 14 (1943-1945), p.5-72, in part. p.16.

[10] ALBERTUS MAGNUS, Summa de mirabili scientia Dei II, q.69 m.2 a.1, Ed. Borgnet 33, p.11a. Cf. É. GILSON, “L’âme raisonnable”, cit., p.13.

[11] ID., De anima l.3 tr.2 c.11; ibid. l.3 tr.2 c.12, p.193, 93 sqq.; ibid., l.3 tr.3 c.14, p.227, 72-80.

[12] B. CARLOS BAZÁN, “The Human Soul” cit., p.111.

[13] A. MAURER, Medieval Philosophy. An Introduction (second edition with additions, corrections, and a bibliographic supplement), Pontificial Institute of Medieval Studies: Toronto 21982, p. 156. Cf. footnote 1.

[14] ALBERTUS MAGNUS, De natura et origine animae, tr.1 c.8, Ed. Colon. 25/1, p. 17, 18-24: Sed melius dicitur esse intellectualis natura composita ex eo quod est de natura sua intellectuale, et ex eo quo est perfectio intellectus. Cf. De homine, q.55 art.4 p.1, solutio, Ed. Borgnet 35, p. 470а.

[15] ID., De nat. et orig. an., tr.1 c.5, p. 13, 64-14, 43; cf. ibid. tr.1 c.4, p.10, 90sqq.

[16] Ibid., tr.2 c.6, p.27, 46-48; ID., De anima l.2 tr.1 c.4, Ed. Colon. 7/1, p.70, 48-65. Cf. ARISTOTELES, De anima II, 2, 413 b 9, p.73.

[17] ALBERTUS MAGNUS, De nat. et orig. an., tr.1 c.8, p.17, 32-43. Cf. Super Dyon. De cael. hier. c.4, Ed. Colon. XXXVI, p.66, 4-9.

[18] ID., De anima, l.3 tr.3 c.11, p.221, 61-66 et 222, 3-9.

[19] THOMAS AQUINAS, In II Sent., dist. 19, q. 1, art. 1, ad 4, Ed. Paris. 2, p. 483-484: “anima rationalis praeter alias formas dicitur esse substantia, et hoc aliquid, secundum quod habet esse absolutum, et quod distinguitur; quia anima potest dupliciter considerari, scilicet secundum quod est substantia, et secundum quod est forma”.; Id., In I Sent., d.8, q.5, a.2. Cf. M. LENZI, “Alberto e Tommaso sullo statuto dell’anima umana”, in AHDLMA 74 (2007), p.27-58, in part. p.29; B. CARLOS BAZÁN, “The Human Soul” cit., p.112.

[20] THOMAS AQUINAS, In Metaph., V, 6, ed. Marietti, n.903-904: “Et hoc est quod est hoc aliquid, quasi per se subsistens, et quod est separabile, quia est ab omnibus distinctum et non communicabile miltis.”; ID., Sententia libri De anima, II, 1, Ed. Leonina 45/1, p.69, 102-104: “Dicitur enim hoc esse hoc aliquid aliquid demonstratum quod est completum in esse et specie, et hoc compete soli substantie composite.”

[21] ID., Quaestiones disputatae de anima, q.1, sol., Ed. Leonina 24/1, p.8, 217-250.

[22] Cf. ARISTOTELES, De anima I, 1, 403 a 1-20.

[23] THOMAS AQUINAS, Quaestiones disputatae de anima, q.1, sol., p.9, 269-289: “anima est hoc aliquid ut per se potens subsistere, non quasi in se habens completam speciem, set quiasi perficiens speciem humanam u test forma corporis”.

[24] Cf. J. MARENBON, Medieval Philosophy, and Historical and Philosophical Introduction, Routledge: London-New York 2007.

[25] THOMAS AQUINAS, Summa contra Gentiles, IV, 79, ed. C. PERA, P. MARC, P. CARAMELLO, Taurini-Romae 1961-1967, vol.3, §4135, p.391.

[26] BONAVENTURA, In II Sent. (Opera Omnia, Ad claras aquas, 1882, 1889), d.30 a.3 q.1.

[27] Ibid., d.17 a.1 q.2, resp.: “anima rationalis, cum sit hoc aliquid… habet intra se fundamentus suae existentiae”.

[28] Ibid., d.17 a.1 q.2, resp.: “anima rationalis, cum sit hoc aliquid… habet intra se fundamentus suae existentiae”.

[29] BONAVENTURA, In II Sent., d.17 a.1 q.2, ad 6.

[30] BONAVENTURE, In I Sent. prol. 9.1 ad 5m; 2c (ed. Quaracchi I 8b).

[31] In a significant way, Albert declares his intention to comment on the whole Aristotelian corpus: ALBERTUS MAGNUS, Physica, l.1 tr.1 c.1, p.1, 48-49.

[32] Cf. C. STEEL, Der Adler und die Nachteule. Thomas und Albert über die Möglichkeit der Metaphysik («Lectio Alberina» 4), Aschendorff Verlag: Münster 2001, p. 1-43, in part. p. 19-26.

[33] ALBERTUS MAGNUS, De animal., l.22 tr.1 c.5: “solus homo est nexus Dei et mundi: eo quod intellectum divinum in se habet et per hunc aliquando ita supra mundum elevator […]

Philosophia 1/2012, pp. 90-100