Haldane and Putnam on Formal Cause: Connections with Aquinas
This section incorporates several insights on formal cause gleaned from the exhaustive writings of Haldane on major issues in Aquinas’s philosophy of mind. The discussion above on form and structure in Aristotle and Aquinas illustrates Haldane’s conviction that there is ‘no epistemology without ontology’. Haldane further suggests that there is a different architectonic of proceeding in Aristotle and Aquinas from what one finds in most modern philosophy, in which the former focuses attention on the need to explain rather than to offer justification in the mode of foundationalist epistemology. Haldane has suggested the importance of form for contemporary philosophy of mind, and takes his cue from the work of three philosophers who defend some version of direct realism: Davidson, McDowell, and Putnam. From Davidson, Haldane accepts ‘the anomality of the mental’, which suggests the non-reducibility of the psychological to the physical. From McDowell and from Putnam, Haldane accepts the double claim that any form of representationalism is false and that efficient causation alone is insufficient to explain the possibility of knowledge. These positions are two sides of the same coin. In his analysis of contemporary philosophy of mind, Haldane bluntly argues: ‘I will proceed boldly and suggest that progress (in the philosophy of mind) may be achieved by making use of the ancient doctrine of hylomorphism.’
Clearly input from the world is relevant and is in part at least a matter of efficient causation. However, if there is to be the sort of conformity of mind to thing which Putnam and McDowell seek, then I can only see this being provided according to an account of the sort developed by Aquinas when he writes that the intellect in act is the intelligible in act; or less scholastically, that a thought will only be of a thing when it is formally identical with it; when what we think and what is thought are the same. 
This is nothing other than a statement of what Aquinas proposed, and what later philosophers, under the influence of Brentano, have called a theory of intentionality incorporating the fundamental relationship of ‘tending towards’ or ‘aboutness’ for the object. The principal statement of Aquinas’s theory, accordingly, is that knowledge is the ‘having of a form of another without its matter’ and the ‘receiving of a form without matter’. This is the ontological ground for distinguishing esse naturale from esse intentionale?9
Intentionality theory in Aquinas requires that the capacity to know be considered a ‘primitive’ in one’s ontology of knowing, which is rooted in a subject capable of cognitivity. ‘Taking on the form of another without matter’ entails that there is an isomorphism of structure between the form of the thing and the form as known in the mind. To reiterate briefly: one must take Aquinas literally here—there is a strict, formal identity of form between the knower and the known. This refers to Aquinas’s meaning when he claims in several texts: ‘Sensus in actu est sensible in actu and ‘Intellectus in actu est intelligible in actu. What makes knowledge possible is that the form known is identical with the form in the thing. This holds for both sense knowledge and intellectual knowledge. Haldane writes the following about this set of claims:
What does this mean? And how is it possible? It means that when I think of something, that which makes my thought to be the kind of thought it is [...] is formally identical to that which makes the object of my thought to be the kind of thing it is. [.] The form of dog (what I would call the foundation for the natural kind of dog) exists naturally and substantially (in esse natu- rale) in the dog, and intentionally and predicatively (in esse intentionale) in the thought.
Haldane argues, endorsing the positions offered by Putnam and McDowell, that efficient causation alone cannot explain the possibility of knowing things in the external world: ‘the difficulty is insurmountable so long as one is confined to efficient causation.’ Haldane is troubled that, while McDowell approaches direct realism, he falls short in explaining how the object as known is the content of the mental act of awareness. This too is Aquinas’s concern; this is where the formal cause as a necessary condition enters the picture. Haldane acknowledges that ‘McDowell is concerned to present a form of direct realism in opposition to views that embody one or another form of epistemological dualism’. Haldane comments on this worry: ‘However, McDowell’s way of viewing the issues is Wittgensteinian in inspiration, and unlike the medievals with their accounts of intentional existence (esse intentionale) he has little to say about the metaphysical structure of the relation between thought and its objects.’ To remedy this lack in McDowell’s analysis, Haldane, like Thomas, calls for the role of formal cause as a necessary condition in order to explain how the mind indeed knows the world.
Sellars and Haldane argue that some position on formal structure is a necessary condition; otherwise scepticism, following from a causal theory of perception rooted in efficient cause alone, is unavoidable. To avoid this consequence requires some account of formal cause. Therefore, within analytic philosophy itself—from Nelson’s synthetic necessary causal connections of causality and from Sellars’s and Haldane’s requirement of form as a necessary condition for the isomorphism needed to explain the possibility of knowing, to Bergmann’s accepting of sortal properties in an Aristotelian mode—it is apparent that the concept of form in matter, especially as found in the writings of Aquinas, is not irreconcilable with the requirements of contemporary analytic ontology and philosophy of mind. This justifies a reconsideration of a causal theory of perception in terms of formal cause. Formal cause, moreover, is never reducible to efficient cause.
-  John Haldane, Form and Matter: Themes in Contemporary Metaphysics, ed. David S. Oderberg(Oxford: Blackwell, 1999), 41.
-  Ibid., 54.
-  Geach and Kenny often emphasized the ontological differences between esse reale/naturale and esseintentionale.
-  John Haldane, ‘A Return to Form in the Philosophy of Mind, in David S. Oderberg (ed.), Form andMatter: Themes in Contemporary Metaphysics (Oxford: Blackwell, 1999), 54.
-  Ibid., 56.
-  John Haldane, ‘Rational and Other Animals, Royal Institute of Philosophy Supplement 41 (1996), 22.
-  Ibid.