Organ as Vehicle
In offering an analysis of Aquinas on sensation and perception, both Kenny and Haldane discuss the concept of ‘vehicle’. Both philosophers seek to articulate the differences between what this chapter refers to as a disposition, its exercise or actuality, and the person serving as the ground for this cognitive ability. Kenny writes: ‘In addition to an ability and its exercise and its possessor, we may introduce the notion of the vehicle of an ability.’ It appears that what Kenny signifies with the term ‘vehicle’ is what this chapter has identified as the organ of the faculty. Kenny continues: ‘The vehicle of an ability is the physical ingredient or structure in virtue of which the possessor of an ability possesses the ability and is able to exercise it.’ In a more recent essay, ‘Cognitive Scientism, Kenny offers the following account of a vehicle: ‘The vehicle of a power is the abiding actuality in virtue of which a substance possesses a potentiality that finds expression in transitory exercises. This underlying actuality may be an ingredient, or a property or a structure.’ Kenny suggests that Aquinas does not make this distinction. Kenny then offers a somewhat conflated observation on this set of issues: ‘([Aquinas] frequently distinguishes between an ability and its organ, which is a particular kind of vehicle: roughly speaking, a part of a vehicle subject to voluntary control.’ It is unclear how a sense organ, as a kind of vehicle, is under a perceiver’s voluntary control. As Berkeley once noted, when a person opens his eye, he cannot but see what is directly in front. Kenny also discusses this concept in his The Metaphysics of Mind: ‘A vehicle is something concrete, something that can be weighted and measured. An ability, on the other hand, has neither length nor breadth nor location. This does not mean that an ability is something ghostly: my front door key’s ability to open my front door is not a concrete object, but it is not a spirit either.’ This passage too appears to suggest that there is a material grounding for a sense faculty, which this analytic study offers as the category difference between an organ and a faculty. Certainly, every case of a sense faculty, both external and internal, requires a vehicle that is the material grounding for the faculty’s ability to exercise its proper function. A Cartesian immaterial spiritual res cogitans and Aquinas’s person are neither identical nor coextensive. One recalls Aquinas’s significant non-Cartesian passage discussing the nature of a human person: ‘Anima mea non est ego.’ This material embodiment of the human anima—the substantial form as the structure—cannot function independently of a material grounding. This is the import of the vehicle as this material grounding for sense organs.