Author: Helen Hattab
Part of: Francisco Suárez’ Philosophy of Nature (coord. by Simone Guidi)
Peer-Reviewed: Yes
Published: May, 27th, 2020
DOI: 10.5281/zenodo.3858140

The latest version of this entry may be cited as follows: Hattab, Helen, “Suárez – Hylomorphism and Body-Soul Composition”, Encyclopedia, Mário Santiago de Carvalho, Simone Guidi (eds.), doi = “10.5281/zenodo.3858140”, URL = “”, latest revision: May, 27th, 20120.


In contrast to our post-Cartesian image of the philosopher as a lone genius who boldly casts all tradition aside and employs nothing but the individual mind’s eye to lay the foundations for a new philosophical system, Francisco Suárez was a participant in a centuries long, multi-faceted intellectual conversation centered round Aristotle’s works and the theological, philosophical and interpretive questions they raised in a variety of cultures and intellectual contexts. Suárez’s views on hylomorphism and the body-soul composition can thus not be neatly separated from debates among predecessors and contemporaries who likewise contributed to the rich complexity of questions, arguments and solutions developed within the broader framework of Aristotelian hylomorphism. Hence, I first attempt to situate Suárez’s views within this broader framework before I focus on how he responds to his main interlocutors on a subset of issues. However, since 16th century Aristotelian philosophies are still relatively understudied, I make no claim to provide a complete account of Suárez’s hylomorphism, much less so his contributions to centuries of discussion. This article is intended as a starting point, inviting further inquiries, elaborations and amendments.

General Features of Sixteenth Century Hylomorphism

Suárez shares with most 16th century philosophers a commitment to Aristotelian substance theory. For Aristotelian philosophers of this period, the fundamental realities are primary substances, like this person, this flower, this cat, each of which is a distinct numerical unity. Hylomorphism is the view that natural substances are compounds of two more basic principles: matter and form. Matter and form are not physical parts; hence a primary substance is a genuine unity rather than an aggregation of parts. The matter of a natural substantial unity is typically the material a thing is made up of; its form is what gives the substance its characteristic structure, features, functions and activities. Aristotle illustrates this with the example of a statue. The bronze or marble it is made of is its matter, whereas its shape and function (e.g., a likeness to honor Athena) is its form. In nature, the matter of a human being would be her flesh and bones; her form is how these are arranged and structured to fulfill the life functions of this type of organism. But flesh itself has form, its matter consisting in more basic materials suited to become the soft, flexible tissues of muscle, tendons etc. and differing from those basic materials suited to taking on the form of hard, inflexible bones. Aristotelian matter is thus not primarily a specific material, but rather corresponds, at each level, to a certain capacity or potential to take on some forms and not others. Matter is relative to form. What is the matter of the ultimate materials constituting the materials that make up flesh and bone? At a certain point one arrives at the most basic elements, for an Aristotelian, earth, air, fire and water. These can also be analyzed into matter and form.

The matter of elemental forms is called prime matter by some interpreters of Aristotle. Since matter for Aristotle is always matter of something, it is at root the capacity to take on a certain form. What then could the most basic matter be, other than the sheer potential to take on any form? On one influential interpretation, held among others by St Thomas Aquinas, prime matter thus does not exist without form. Prime matter, since it is formless, is on this view a pure potential that is only actualized and caused to exist by form. Though Jesuits were bound by the Ratio Studiorum to follow Aquinas’s theology on non-controversial issues, in the late16th century, his view of prime matter begins to fall out of favor among Jesuit philosophers. By the end of the century, arguments against Aquinas’ view by late medieval philosophers, like Henry of Ghent and John Duns Scotus, had won out. Suárez as well as contemporaries and successors, both Catholic and Protestant, argued that prime matter is an entity, which could be conserved by God without form. (Hattab, forthcoming) Suárez concludes against the Thomists that both prime matter and the substantial form that informs it are incomplete or partial substances capable of being conserved in being, independently of one another. Matter actualized by form is a complete substance, i.e., a primary substance, like Queen Elizabeth, the dog sitting on her lap, and the pearl hanging from her ear.

For Suárez, as for other 16th century Aristotelians, the first form that informs prime matter and with matter composes a substance, is called the substantial form. This form is the root of both accidental forms and essential properties we invoke to identify and define substances. Elizabeth’s substantial form makes her recognizable as a human being, distinct from the dog sitting on her lap, or a robot made to look exactly like her. Her substantial form also supports certain non-essential properties or accidents associated with her at different times; e.g., her red color is an accidental form in her hair distinct from the reddish hue found in and dependent on the fur of the dog on her lap. Unlike the robot made in her likeness, Elizabeth sometimes displays accidents in the category of passion, such as anger, fear and joy and these can affect the rational thinking essential to humans. Suárez takes the interdependence of otherwise distinct features of a substance to indicate that the substantial form unifies the accidental forms of a substance.

Elizabeth’s substantial form must be more than the shape and the organization of her bodily parts in order to be the bearer of multiple other forms that distinguish her from a statue or robot modeled after her. For Aristotle and his followers what primarily defines things in nature, especially living things, are their characteristic activities. Forms in nature are not static. In this sense, Aristotle’s example of the statue’s shape is misleading. The statue is after all an artificial substance, as is the robot made in Elizabeth’s likeness. In natural substances form is rather a pattern of self-activating, goal-directed activity realized by the capacities of the material parts working together. For example, the form of your and my bodily parts consists in the range of activities a fully functional human being can realize, from digestion to moving around and sensing, all the way up to reasoning and contemplating truths. The way Aristotle puts it is that form actualizes the powers of the matter. Except for purely intellectual thought, which Aristotle claims requires no bodily organ, form is not something physically separable from matter: it is the actuality or activity of the potentialities that constitute matter. When that activity reaches the capacity for self-change, the substance is said to be alive. Hence the substantial form of a living substance is called a soul. Hylomorphism when applied to living things thus entails that biological substances are compounds of a body capable of life and a soul, conceived as the readiness to engage in all the life activities of that kind of substance: in the case of plants, a vegetative/nutritive soul, in animals a sensitive/perceptive soul and in humans a rational/intellective soul.

Thus far I have outlined some core metaphysical commitments that Suárez shares with 16th century philosophers we label as ‘Scholastic Aristotelians’, in general, and with his Jesuit colleagues, in particular. However, that is not to say that Scholastic Aristotelians were slavish followers of Aristotle who agreed on everything. For the entire chronological and geographical span of the Aristotelian tradition, one finds sharp theological, philosophical and interpretive disagreements on many issues. It is impossible to appreciate Suárez’s contributions without situating the way he develops hylomorphism within the broader Aristotelian tradition. During the medieval and renaissance periods, increasingly complex accounts and interpretations of the substantial form plus its relation to prime matter were developed to address theological constraints, philosophical problems as well as inconsistencies and lack of clarity within Aristotle’s texts. I now outline some known debates that Suárez weighs in on.

Disputed Questions Generated by Hylomorphic Theories

One pressing theological question driving developments in hylomorphic theory concerned the status of matter. Was prime matter an entity in its own right, which was created by God, or was it merely concreated (co-created) with the creation of a substance, as Aquinas had argued? Another thorny issue bearing directly on hylomorphism was the need to account for the separability and immortality of the human soul while preserving its role as the human substantial form, which constitutes a substantial union with a person’s body. This issue received renewed attention after 1516 when Pietro Pomponazzi published On the Immortality of the Soul, arguing that the immortality of the soul could not be defended philosophically. A compelling case has been made that Suárez’s arguments for the immortality of the rational/intellective soul in his Commentary on the De Anima are structured to respond to Pomponazzi’s argument though Suárez is careful not to name him (South 2012). Below I show that Suárez’s solutions to these theological issues involve novel philosophical metaphysical positions on the nature of matter, the nature of the soul/substantial form of a human being, and their union.

Suárez also weighs in on some longstanding philosophical questions concerning the nature and role of Aristotelian forms. First there is the question whether there is only one substantial form per substance (the unitarian view) or a plurality of forms for each natural substance. The need to account for the fact that a corpse retains the recognizable accidental forms of the dead individual for some time, and that a human being has distinct nutritive, sensitive and intellectual powers prompted some 13th and 14th century philosophers to reject Aquinas’ unitarian view. Rather than posit a forma cadaveris, to enter the matter as the human soul left it, some argued that in addition to the soul, there was a form of the body which remained for some time after death. Suárez rejects both the form of the cadaver and the form of the body, arguing instead that certain accidental forms inhere directly in the matter of the body thus accounting for the integrity of the corpse for some time. Dennis Des Chene discusses the details, philosophical implications and historical significance of this view of matter (Des Chene 1996: ch 5).

In addition to positing a distinct form of the body, some philosophers, like William of Ockham also posited distinct substantial forms for the nutritive soul, the sensitive soul and the rational soul. Such pluralist views created the need to account for the genuine unity of a substance with more than one substantial form. (Lagerlund 2012: 473-474) On this question Suárez upheld the Thomist unitarian view, though as we shall see, his divergence from Aquinas on other key issues pushes him to reformulate the nature of the soul-body union. Another type of philosophical puzzle stemmed from the standard doctrine that all substantial forms, except the immortal rational soul are educed from matter, rather than created and joined to the body by God. Suárez addresses problematic implications of this doctrine for the coming into being of forms, and the role that accidents of matter play in educing from matter the substantial forms of non-human corporeal substances. As I show elsewhere, his solutions are more consequential than they might seem. (Hattab 2012: 110-111, 115-117)

Problems arising from Aristotle’s texts included his account of the transmutation of the four elements in On Generation and Corruption, which implied that the prime matter underlying them was corporeal and extended, whereas other texts characterized it as incorporeal and unextended. The Islamic commentators, Avicenna and Averroes, following the ancient Greek commentator Simplicius, thus posited a corporeal form inhering in prime matter. (Hyman 1965: 1-2) Aquinas and his followers denied any form common to all matter – the first form is the individual substantial form of the composite. However, Scotus, argues for a form of corporeity that an individual body retains when the soul departs. In addition to above-mentioned philosophical and textual considerations, Scotus is driven by the need to account for the fact that the bread consecrated by Christ remains Christ’s body even during the three days of his death. (Scotus, Or. IV, d.1, a.1, q.2) The difficulty is that if the first form causing matter to exist is Christ’s soul, then there can remain no flesh and blood of Christ when his soul separates from his body. Attributing multiple forms to individual substances ensures that a form of Christ still informs the bread, namely the form of corporeity. Suárez, with the Thomists, denies this form, while maintaining with the Scotists that prime matter is an incomplete substance that has its own being and could be conserved by God without the substantial form. Suárez’s combination of Thomist and Scotist doctrines has important implications which I discuss in the following sections.

Another tension within Aristotle’s texts concerned the principle that individuates natural substances. There is textual evidence both for the Thomist view that matter individuates, and for the Averroist view that form individuates, as well as for the view of some renaissance commentators that form and matter together individuate natural substances. The problem of individuation further informs the way in which various 16th century philosophers account for the nature of the specific and generic forms that are the basis for our abstract universal concepts. Suarez’s arguments on form thus have consequences for his theory of universals and hence influence whether we interpret him as a nominalist or realist on universals. (Akerlund 2009) How best to classify Suarez is still heavily debated, illustrating how much is still unknown about developments in 16th century hylomorphism and their connection to the positions Suarez and his interlocutors take on key metaphysical and epistemological questions. (Heider 2014: 88) Suárez’s contribution to the metaphysics of universals, though significant and relevant to early modern philosophy, is beyond the scope of this article and will be the subject of a separate work.

Suárez on the Nature of Prime Matter

To understand Suárez’s hylomorphism and account of the body-soul composition one must first understand his accounts of prime matter and the substantial form. Suárez appears to have been part of a shift in late 16th century Jesuit philosophy away from Aquinas’ account of prime matter as a pure potentiality which receives its existence from the formal cause of the substance, namely, its substantial form. Aquinas defends the position that to be created is proper to composite and subsisting things (things that exist independently rather than inhering in something else). (Aquinas, ST I, q. 45, art. 4, 468) Accordingly, for Aquinas, prime matter is not created but rather concreated when God creates a substance ex nihilo. But this view produces various problems. First, if prime matter is not properly created by God then neither can divine grace be since it too is not a subsisting thing. Second, simple bodies cannot be properly created since they are not composite. Finally, the mystery of the Incarnation also seems not to be a case of proper creation, because Christ’s humanity does not subsist per se but in a Word and Chris is generated in the uterus of Mary from pre-existing matter. The need to reconcile these theological doctrines with an Aristotelian account of prime matter drives late 16th century Jesuit theologians and philosophers to gradually move away from Aquinas’ view of prime matter. Though Luis de Molina still traces the origin of prime matter to God’s concreation and denies that the Incarnation is a case of creation proper, Gabriel Vasquez loosens the conditions for creation proper to allow for all things that are not dependent on a subject by nature to be properly created, even if they are not actually subsistent. This allows Vasquez to count the origin of prime matter and the Incarnation as instances of proper creation. The Coimbran commentators, Suárez and Hieronymus Fasolus go one step further, arguing that prime matter is a subsisting, albeit partial and incomplete entity which, though it does not naturally exist without form, could be conserved by God without form. This prompts them to define prime matter as something with its own essence and existence, though they still conceive of it as the potentiality for form. (Hattab, forthcoming)

Suárez defends this view in different texts. In his highly influential Metaphysical Disputations he argues for the conclusion that “Matter has a proper act of existing …” on the ground that “It has a partial and proportionate act of subsistence, for no doubt it needs that so that it could be a first subject”. (Suárez, D.M. XIII, s. 5, n. 8) Hence like Vasquez, Suárez bases his reasoning on the fact that prime matter depends on no other subject, but unlike Vasquez, he infers from this that prime matter must have its own act of subsistence, i.e., an act of existing, at least partially, independently of form. Hence, Suárez preserves Aquinas’ criterion that properly created things must be self-subsisting but against Aquinas, attributes to prime matter, the first subject of natural things, true subsistence as a partial substance. Suárez does not discuss question 45 in his work on the Prima Pars summa theologiae de Deo Uno & Trino. However, he reinforces the view that matter has its proper entity, proper entitative act and proper being in Book III, chapter 5 of this work, which is devoted to the question, “Whether in the divine practical scientific knowledge [scientia] there are ideas of all creatures, and how many and of what kind they are?” (Suárez, 1607: Bk. III, cap.5,156b) Suárez claims that God has ideas, or divine exemplars of all things, which he made or could make, per se and properly. It follows that God has an idea of every individual complete substance or supposite. However, Suárez points out that theologians disagree whether there are ideas in God of the parts of substance, especially prime matter. Aquinas and Cajetan deny that God has a proper idea of prime matter on the grounds that “matter has neither being nor actuality except through form, whence it cannot come to be known unless with it and through the idea or account of the whole” (Suárez 1607: Bk III, cap.5, n.12: 158b). Suárez finds Albert the Great’s view the most pleasing and affirms with him that prime matter is known distinctly by its proper concept since it has its own proper being, and also comes to be and is conserved by a proper creative and conservative action (Suárez 1607: Bk III, Cap.5, n.13: 158b ). In short, the view that prime matter is a subsisting thing not only makes it easier to reconcile Aristotelian substance theory with several theological doctrines, but it also makes prime matter capable of being known distinctly via its proper concept in God.

Given that form and matter are closely related as potency and act in Aristotelian substance theory, and given that the substantial form, on Suárez’s unitarian view, is the sole primary form actualizing the prime matter, composing with it a distinct, numerically one substance and serving as the root of all other forms the matter can take on, Suárez’s departure from Aquinas’ doctrine of prime matter entails a rethinking of the nature of the substantial form. One of the most significant changes Suárez makes to the Thomist account of the substantial form is that such forms can no longer be the formal cause of substance in the sense that by actualizing the pure potential that is prime matter, they cause the matter to exist. Rather, since matter has its own proper existence independently of form’s actualization of its potentials, formal causality must be reconceived. This has important implications for how Suárez conceives of the body-soul union, which will be examined in the last section. First, I lay out Suárez’s account of the substantial form.

Suárez on the Substantial Form

In Disputation15 Suárez does not follow the standard Scholastic procedure of arguing for the existence of the substantial form from the distinction between generation simpliciter of corporeal entities and accidental changes, such as a body becoming white or cold. Instead Suárez builds up his argument for the substantial form from the immortality of the rational soul. He first infers that the rational soul is a substance not an accident for how else could it survive without the subject in which it inheres? At the same time, it must be the true form of the body for if it were not, it could not cause the body to live nor would the life functions of a person cease once its union with the body was dissolved. Therefore, he concludes, the rational soul must be both a type of substance and the form of the matter that is the human body. He resolves the apparent conflict involved in the soul’s being both a substance and a form by claiming: “Therefore, this soul is a substantial form for, as we will show below, the name “substantial form” signifies nothing other than a certain partial substance which can be united to matter in such a way that it composes with it a substance that is whole and per se one, of which kind is a human being.” (Suárez, D.M. 15, 1, 6, vol.I: 499) Later Suárez clarifies the phrase ‘partial substance’ stating: “Form is a certain simple and incomplete substance which, as the act of matter, constitutes with it the essence of a composite substance.” (Kronen & Reedy 2000: 77) Hence, the substantial form, like prime matter is an incomplete substance, only it is actuality whereas prime matter is potentiality. Just as prime matter subsists and could be conserved without form by God, the substantial form can exist without the matter of which it is the act. The thrust of Suárez’s argument is to begin with the premise that the rational soul, as the substantial form of the human body, is both immortal and the body’s act; from this he infers what must be true of any substantial form to meet these twin requirements.

Suárez’s definition of the substantial form as an incomplete substance diverges from Aquinas’ account of it as the essential act of existing whereby the purely potential prime matter is caused to exist. Suárez’s definition appears to give all substantial forms the independent status that Aquinas granted to only the immortal soul. For Aquinas, the human soul is an exceptional kind of substantial form. Unlike the rest, it is the principle of intellectual operation. The intellect cannot have a corporeal nature for this would prevent it from knowing all bodies; therefore, the soul must be incorporeal. Moreover, it must be subsistent for only self-subsisting things can have their own proper operations. In response to the objection that only something that is said to be ‘this particular thing’ can subsist, Aquinas distinguishes between two different senses of ‘this particular thing’. First anything subsistent, even a separable part of a substance like a hand, can be called ‘this particular thing’. In the second sense, only things which are “complete in a specific nature” like the composition of soul and body count as particular things. The second sense thus excludes parts, accidents, and material forms of composite substances. Nonetheless, the first sense of ‘this particular thing’ allows the intellectual soul, as a part of the human nature, to count as a particular thing or a substance-like entity in the way that a severed hand could be regarded as such. (Aquinas, ST I, q. 74, a. 1-3) However, all other substantial forms are neither particular things nor separable in this way.

In Suárez’s account an important switch has occurred: the immortal rational soul is not the exception, but rather the paradigm of all substantial forms. Given that Suárez has already broadened the range of subsisting things to include prime matter, he can likewise include all substantial forms, even those of inanimate bodies, plants and non-rational animals under the umbrella of incomplete substances that subsist. To subsist is merely to be capable of being conserved without the corresponding form or matter by God, even if this never occurs naturally. Every substantial form is thus an incomplete/partial substance that could exist without the body. As I have demonstrated elsewhere, this is precisely the account of the substantial form René Descartes targets when he writes the following. (Hattab 2009: 24-64)

For lest there be any ambiguity in the term, it must be noted here that by the name of the substantial form, when we deny it, is understood a certain substance joined to a certain matter, and with it composing a certain merely corporeal whole. And this [form] no less than matter or even more than matter is a true substance, or self-subsisting thing, since it is certainly called Act, the latter in fact only Potency. (Descartes 1996: Vol. IV, 502)

A key legacy of Suárez’s hylomorphism is that in developing the foundational Aristotelian metaphysical doctrines of prime matter and substantial form, he made possible subsequent attacks by Descartes and others on all substantial forms as mysterious, soul-like entities that are unnecessary to explain natural phenomena. The substantial form survived these attacks only in its more restricted role of the intellective form of the human body.

Suárez on the Body-Soul Union

Another significant consequence of Suárez’s view is that the substantial form can no longer function as the formal cause of the being of the matter. The matter must already exist and be something for it to contain the powers that when acted on by the agent cause will produce the composite. Hence, Suárez must reject Aquinas’ equation of the substantial form with the formal cause of the being of matter. For Suárez, the substantial form is strictly the form of the matter-form composite. As incomplete substances, both matter and form could be created and conserved by God without the other even though, in nature, God does not sustain matter without form. However, Suárez makes clear in section five, paragraph 2 of Disputation 15, that the substantial form, though a substance in its own right, is always intended for matter in the sense that it is an act of matter—either one that actually informs the matter or (in the case of the rational soul) one that is prepared by its nature to inform matter. Suárez thus tries to maintain the complementarity between form and matter to preserve the genuine unity of a substance, despite their intrinsic separability.

In the next section Suárez reconceives the nature of formal causality to fit his recasting of the relationship between the substantial form and the matter it informs. The formal causality of the substantial form now consists simply in its union with the matter. There are two different kinds of union depending on the type of substantial form involved. The first is the pure union that the rational soul forms with the body. Such a union does not involve the form’s inherence in or dependence on the matter and was thought by Henry of Ghent, among others, to come from the soul alone. In other words, God creates the rational soul in a properly disposed body and the soul immediately unites itself to the body by natural inclination. The major objection to this view is that since it arises directly from the soul’s natural impulse, a pure union consists in efficient causality not formal causality. Suárez responds that it is uncertain whether the union is produced by the soul alone. However, even if one held this view of its production, there could still be a formal bond which, in addition to the efficient causality involved, joins the soul to the body. The implication is that, in this case, the formal bond would be the formal causality.

Non-rational substantial forms are more problematic as in this case there is not a pure union with the body but one which involves a dependence and a quasi-inherence of the form in matter. This presents an obstacle to accepting the view that the formal causality of a substantial form consists simply in the formal bond of such a union, since non-rational substantial forms are effects of the union and therefore dependent on it. Thus, the objection runs, such substantial forms cannot be the cause of the union and hence cannot constitute the causality of the formal cause. Suárez responds that since the union is the joining of matter and form, it constitutes both the material and formal cause: the union is both the road from matter to form and from form to matter. To the objection that this undermines the priority by nature of the formal cause, Suárez responds that this follows only on the assumption that ‘union’ refers to the action producing the union. He suggests instead that this action is more properly called ‘unification’ in order to avoid confusion with the union itself. Properly speaking the ‘union’ is “the mode of union or inherence which remains between matter and form in the being which has been produced.” (Suárez, DM, XV, s. 6, n. 10, 1: 521) Suárez acknowledges that the non-rational substantial form which is educed from the potency of matter could not be the formal cause of the action by which it is educed, for such a form is the end point and not the starting point of that action. He concludes that when speaking of the formal cause, “We are speaking, therefore, about the mode of union, which has a far different nature, because it is not actively related to the form, but is, as it were, a formal nexus between the form and the matter and therefore, it can have dependence upon each, as has been said.” (Suárez, DM, XV, s. 6, n. 10, 1: 521–2) So formal causality boils down to the manner in which matter and form comprise a union. In non-rational substances, the way the two are connected is not a product of the form but can depend on both the form and the matter.

For Suárez, prime matter thus depends on form naturally, without the substantial form being the formal cause of the being of prime matter. As he puts it, there are two ways in which matter could depend on form: by a dependence on a proper cause or by a dependence on a condition so necessary that without it, being is not owed to the thing. Suárez presents arguments in favor of both views but notes that the second view has the advantage of reconciling two conclusions already established: that the form is not the formal cause of the matter and that matter (naturally) depends on the form for its being. In defending the second view, Suárez argues that matter depends as a necessary condition on quantity; therefore, it can likewise depend in this way on form. Accidental forms, like quantity, are dispositions necessary by way of conservation, not because they are proper and direct causes of the conservation of substance but because they are such natural dispositions that they are necessary. E.g., just as oxygen is necessary to my physical survival, while not causing me to be born and be me, the sizes and shapes of my body parts are natural dispositions necessary to preserving me, even though they do not cause my existence (e.g., the particular size and shape of my lungs allow me to breathe). As a result, the substantial form or its union with matter, and thus the whole composite substance, depend on accidental forms, as these kinds of dispositions, to be conserved in existence. To an even greater degree then, matter once it is created, also depends for its continued natural existence on the substantial form as on a necessary and primary disposition, not as a cause. (Kronen & Reedy 2000: 107-108) Note that this moves the substantial form out of the realm of Aristotle’s four causes and reduces its role to a necessary condition, on a par with the role that accidental forms play in the continued existence of a substance.

The upshot of all this is that in Suárez’s hands the substantial form and its role in the soul-body union have been transformed into something quite different from what we find in Aquinas and his followers. First, the substantial form is not an act of existence perfecting matter and causing it to be. Rather it is an incomplete substance, which through the mode of its union with another incomplete substance (matter) constitutes a complete substance. Second, form and matter are equal partners in this union for Suárez. The substantial form is not prior to the matter by its action; it does not even exercise formal causality by its action. Rather the matter depends for its continued existence on the substantial form as a necessary disposition. Third, formal causality no longer springs from a dynamic, emergent form that gives being to matter and orders its potencies to their ends. Formal causality is static, consisting merely in the manner of union that an already existing substantial form has with an already existing matter. All that is required for the union to occur is that these two pre-existing incomplete substances have the requisite “proportion and mutual aptitude” that allows them to immediately unite and produce something that is essentially one. (Suárez, DM, XV, s. 6, n. 2, 1: 518)


Though much remains to be explored when it comes to Suárez’s contributions to hylomorphism, we can make the following preliminary observations from this brief examination. The ways in which Suárez develops Aristotelian hylomorphism promote increased separability of matter and form and a radical circumscribing of the role of the substantial form. These changes entail a redefinition and demotion of formal causality and a consequent weakening of the union between soul and body. It should not then surprise us that both formal causation and hylomorphism itself fell increasingly by the wayside in the 17th and 18th centuries and that new substance theories that attempted to fill the void struggled to account for the unity of natural macroscopic bodies.

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