Volume 80, 2006
Intelligence and the Philosophy of Mind
Formal Identity as Isomorphism in Thomistic Philosophy of Mind
A central problem within an influential strand of recent philosophy of mind has been to explain the “conformity of mind to thing” that characterizes knowledge. John Haldane has argued that this problem can be best addressed by a development of Thomas Aquinas’s account of the “formal identity” of the knowing subject with the object known. However, such a development is difficult to present in a manner perspicuous to a contemporary audience. This paper seeks to present a persuasive account of formal identity, taking sensory cognition of the individual object as the primary case for examination. Formal identity is initially explored using
the notion of encoding, or the systematic transfer of information reflecting efficient and formal causal processes. The mathematical notion of “isomorphism” is then
employed to describe precisely the features of encoding needed for formal identity. Forms are defined as formally identical if and only if they are isomorphic.