One last Ryle post for the day. This was a very odd section in Jason Stanley and Timothy Williamson’s Knowledge How (PDF).
Let us turn from Ryle’s arguments against the thesis that knowledge-how is a species of knowledge-that to his positive account of knowledge-how. According to Ryle, an ascription of the form ‘x knows how to F’ merely ascribes to x the ability to F. However, it is simply false that ascriptions of knowledge-how ascribe abilities. As Ginet and others have pointed out, ascriptions of knowledge-how do not even entail ascriptions of the corresponding abilities. For example, a ski instructor may know how to perform a certain complex stunt, without being able to perform it herself. Similarly, a master pianist who loses both of her arms in a tragic car accident still knows how to play the piano. However, she has lost her ability to do so (cf. also Ziff (1984, p. 71). It follows that Ryle’s own positive account of knowledge-how is demonstrably false.
I’m not where Ryle offers that account. As I read him, Ryle says that knowledge how is, like most mental states, a complex disposition that has no (easily statable) necessary or sufficient conditions. To get a sample of the kind of thing Ryle does think is involved in knowledge how, consider what he says about knowing how to tie a knot.
You exercise your knowledge of how to tie a clove-hitch not only in acts of tying clove-hitches and in correcting your mistakes, but also in imagining tying them correctly, in instructing pupils, in criticising the incorrect or clumsy movements and applauding the correct movements that they make, in inferring from a faulty result to the error which produced it, in predicting the outcomes of observed lapses, and so on indefinitely. (55)
It seems to me that Ryle could quite easily say that the pianist and the ski instructor both have the knowledge how Tim and Jason assign to them, since both of them can imagine how to perform the act, can instruct, criticise and praise pupils accordingly, can infer what’s going wrong in misperformances etc etc. So while these may be counterexamples to the equation of know how and ability, I don’t see how they are counterexamples to anything that Ryle says.