Vehicle Fallacy

Vehicle fallacy is a term coined by Peter Morriss from a point made by Anthony Kenny. Both Morriss and Kenny start from the recognition that power refers to a capacity or disposition, not an event or occurrence. Philosophers who have [Page 685]investigated how we should understand the meanings of such dispositional terms have started with simple natural powers, such as solubility. To say that sugar is soluble in water, is to say (something like) that if sugar is put into water, it will dissolve. Some philosophers and social scientists have not been happy with this, because the property solubility appears to refer to something unobservable and mysterious, like an immortal soul or a Spirit of the Age driving history. So they have thought that any claim that an object has a dispositional property must really be making a different claim: a claim about observable properties. Thus Willard van Orman Quine said that, when we say that a sugar lump is soluble, we are really saying that sugar has a subvisible structure that makes it suitable for dissolving—even though we might not know what that subvisible structure is. Such a structure is what Kenny calls the vehicle of the disposition, and the vehicle fallacy is thinking that any statement that an object has a particular disposition is not really about the object, but about the vehicle that gives rise to the disposition. Quine thinks that disposition statements are not philosophically acceptable unless they can be rephrased, explicitly or implicitly, to be about some vehicle. Kenny and Morriss disagree, and think that disposition statements are perfectly acceptable as they are. As Stanley Benn pointed out, the power to extinguish a flame is possessed by water, wind, and pyrene foam; all these different things have the same power—the power to extinguish flames. Some doubtless have this power by virtue of a subvisible structure; others do not. Similarly, some political leaders have power because of their charisma, others because of the position they occupy in a social organization. The power is the same, but the vehicles differ.

It is important to be clear about what the fallacy is that Kenny and Morriss have identified. They are certainly not denying that sugar's solubility probably is something to do with its molecular structure. Rather, they are merely claiming that one can understand what is meant by saying that an object has a certain dispositional property, without making any implicit inference as to what might be responsible for this dispositional property. And we need to be able to say that it does have this power, before we can launch an inquiry into how it gets to have this power. Thus, the vehicle fallacy is solely concerned with how we should understand the meaning of a dispositional sentence.