Intentionality in Aquinas’s Philosophy of Mind
The first part of this inquiry elucidates the principles presupposed in Thomas Aquinas’s theory of knowledge, which can be classified as ‘principles of intentionality’. Haldane reminds us: ‘the Thomist account of intentionality is more sensitive and more complex than is usually supposed.’ The concept of intentionality is used because Aquinas’s philosophy of mind and epistemology can best be elucidated and understood by contemporary philosophers in terms of a thesis of intentionality. Geach wrote extensively about Aquinas’s distinction between esse naturale and esse intentionale.  Aquinas uses this distinction as a means of rendering a category difference between knowers and non-knowers. In turn, this distinction grounds the position that an intentionality thesis serving as a backdrop offers a fruitful method for analysing the difficult passages in which Aquinas considers the problems of knowledge, mind, and the role of cognitivity in mental agents. This discussion of Aquinas’s theory of intentionality follows much recent work in Aristotelian philosophy of mind.11
Part of the difficulty of reading Aquinas on mind and knowledge lies in the obscure metaphysical language in which the narrative is couched. The principal statement of this theory asserts that knowledge is the ‘having of a form of another without its matter’. In the Summa Theologiae, one finds a straightforward description of a knower in Aquinas’s system: ‘The difference between knowing and non-knowing beings is that the latter have nothing but their own form; the knowing being, on the other hand, is one whose nature it is to have in addition the form of something else, for the likeness (form) of the thing known is in the knower’ (Summa Theologiae, I q. 14 a. 1).
Admittedly this is a difficult bit of philosophical language to analyse and explain. First, the concepts are not expressed in ordinary language. Secondly, and more importantly, to understand these concepts requires an understanding of other concepts from Aristotelian metaphysics that function as presuppositions for Aquinas’s philosophy of mind. The purpose of this section is to lay bare these metaphysical presuppositions, which provide the principles upon which Aquinas constructed his philosophy of mind; the expected result is a better understanding of Aquinas’s account of knowledge, mind, and cognitive agents through the lens of an intentionality theory. The following three presuppositions are fundamental to Aquinas’s theory of intentionality:
A theory of intentionality need not entail a realm of subsistent objects. While it is true that some philosophers—most notably Meinong and, according to Chisholm, the early Brentano—did postulate subsistent obj ects of intentional acts, nonetheless such a postulation is not a necessary condition for a theory of intentionality. In this analysis of Aquinas, intentionality is considered as the set of ontological characteristics distinguishing know- ers from non-knowers. This distinction entails no ontological commitment to subsistent objects. One vexing problem constantly remains with any ontological realm of subsistent entities: it requires extraordinary epistemological gymnastics to account for an awareness of such entities—one need only recall the theory of anamnesis in Plato’s ontology.
A case will be made for the following three propositions:
This does not imply that Brentano had it all correct in interpreting Aquinas on inten- tionality. Several articles in the Nussbaum and Rorty volume suggest similarities and contrasts of the role Brentano’s account of intentionality played in offering differing interpretations of the Aristotelian and Aquinian principles regarding the immaterial reception of forms.17 Haldane argued for significant differences. Like Aquinas, Brentano was an anti-materialist, which is grounded in his thesis of intentionality. Considering Brentano’s account of intentionality, Haldane writes: ‘Nonetheless Brentano’s philosophy of mind does introduce a major problem, viz: that of how to explain the contentfulness of mental states without lapsing into some version of epistemological idealism, or adopting an extravagant ontology.’18 Haldane suggests that a contemporary analysis of Aquinas’s philosophy of mind offers a solution to this vexing set of issues faced by Brentano. Accordingly, one must not make too tight a connection between Brentano’s account of intentionality and Aquinas’s position on esse intention- ale. Following Haldane, Brentano’s classic account of intentionality noted above contains four features distinguishing the mental from the physical: ‘(i) Intentional Inexistence; (ii) Immanent Objectivity; (iii) Reference to a content; and (iv) Direction to an object.’19 Haldane also suggests that the first two characteristics refer to ontological properties of intentionality, while the latter two refer to psychological properties. Both the ontological and the psychological sets of properties are necessary conditions for rendering Aquinas’s account of intentionality consistent and workable. In Psychologie vom empirischen Standpunkt, Brentano characterizes this fundamental intentional property: ‘Characteristisch fur die psychischen Phanomene ist die Beziehung ein Object,’20
This intrinsic capacity of referring or ‘aboutness’ is the cornerstone of intentionality theory, which in turn grounds the externalism in Aquinas’s theory of mind. Given this necessary referring relation, Aquinas cannot be reduced to an internalist. Externalism normally suggests a cognitive theory in which at least some of our ideas and concepts are connected with and dependent upon facts or things in the external world. An internalist, for the most part, will deny this external connection, preferring instead to claim that justification in knowledge depends in some manner on a priori claims that are known immediately and upon which one’s theory ofjustification is constructed. While there are several offshoots of these two theories, nonetheless this account, while schematic in form, provides the background as this narrative on Aquinas unfolds. Simply put, a Cartesian epistemology with its criterion of certainty would be a paradigm case of an internalist position, while Aristotle’s cognitive theory rooted in his De Anima would be an externalist account.
The following propositions apply to Aquinas’s use of intentionality:
In the context of contemporary discussions on the nature of the human mind and its epistemological connection with the external world, Stump argues correctly that Aquinas might best be described as an ‘externalist/reliabilist’; on this point, this study agrees with Stump’s characterization of Aquinas.
At times when considering esse intentionale in discussions of Aquinas on intention- ality, there is confusion between propositions (c) and (d) above. Esse intentionale refers to the cognitive content of the act of awareness; yet this act of awareness and its content depend on an ontological characteristic of the knower, which is a necessary condition for explaining the possibility of knowing. This in turn depends on a holistic theory of the human person with ontologically grounded dispositional properties able to exercise cognitive abilities at the levels of both sense and intellect. Introspection, contrary to the Cartesian paradigm, is not the hallmark of the mental, nor is the reality of a Cartesian immaterial ego a necessary condition for an intentionality thesis.
Haldane suggests correctly that an appeal to what Aquinas scholars call ‘the formal identity’ between the mental act and the object perceived or known—Aristotle’s formal cause—is a necessary condition to move beyond the limits of representative theories of perception. Perspicuously, Haldane then suggests that this formal identity requires the possibility of two distinct kinds of exemplification, one for esse intentionale and the other for esse naturale or reale. This dual account of exemplification is needed in order to account for the possibility of a form existing both in rerum natura as well as in cognitive organs and faculties. In other words, a form in a thing requires an emmattered existence because a form as form cannot exist by itself. Yet the form itself is not material, although its ontological role is for physical objects; the form is exemplified in matter in order for a primary substance—an individual of a natural kind—to exist. In other words, a form in itself—forms in rerum natura—can neither exist nor subsist by itself. This same form, insofar as it is not material per se, can exist intentionally in a cognitive faculty. In this way, Aquinas argues for knowing to be the having of a form without matter in a sense faculty or intellect capable or having the cognitive power of awareness. Hence, this dual notion of exemplification is a necessary condition for unpacking what Aquinas suggests with his theory of intentionality. The two forms—esse intentionale and esse naturale—exemplify two different modes of being, yet their formal structures are identical. Haldane sums up his instructive account of Aquinas in the following perspicuous way:
[This is . . . ] a philosophical theory in which the conceptual structure of our thinking is securely connected to the ontological structure of the world. The character of this connection is of such an order, viz., formal or structural equivalence, as to warrant the title ‘mind-world identity in a description of the theory within which it features.
In Aquinas’s theory of intentionality, the concept of esse intentionale is critically important. For Aquinas, it is apparent that esse intentionale and the property of intentionality in a human knower are connected intrinsically. Put differently, in agreement with an observation put forward by Haldane, esse intentionale indeed constitutes the property of intentionality. This ‘mind/world identity’ determines the meaning of the oft-used Aquinas propositions: ‘sensus in actu est sensible in actu and ‘intellectus in actu est intelligible in actu. The analytic task is to render Aquinas’s ‘doctrine’ of inten- tionality ‘intelligible’. This elucidation of esse intentionale in terms of a unique set of dispositional properties grounding the possibility of intentionality is an example in Aquinas of what Chisholm called ‘a funny kind of characteristic that ordinary physical things don’t have’. Chisholm’s ‘funny characteristic, however, appears referentially opaque. Aquinas, to the contrary, attempts to put ‘cognitive flesh’ on the bare bones of Chisholm’s ‘funny characteristic’. This is analogous to Haldane’s criticism of Putnam’s lack of a ‘metaphysical skull’ when referring to Aristotle’s intentionality. It follows that
Aquinas’s concept of intentionality is a de re claim and never reducible to a de dicto position.