There is a certain puzzle about knowing how which may be put as follows:
Among the many people who know how to get to Philadelphia there is at least someone, we may imagine, who does not know that Philadelphia is the City of Brotherly Love, and, consequently, does not know how to get to the City of Brotherly Love, even though he does know how to get to Philadelphia, and Philadelphia is that city. But the action of getting to Philadelphia is identical with the action of getting to the City of Brotherly Love. Thus, among the many people who know how to get to Philadelphia there is at least someone who both knows how to get to Philadelphia and also does not know how to get to Philadelphia.
How shall we reply to our puzzle? First I shall note certain ways of replying to the puzzle which will not be adequate. And then I shall attempt to set forth a certain theory concerning expressions of the form'S knows how to F' which will make clear what I believe is the proper way to reply to it.
It is clear that we cannot reply to our puzzle simply by asserting that it is impossible for a man to be such that he both knows how to get to Philadelphia and also does not know how to get to the City of Brotherly Love. For after all it is not impossible for a man to be such that he is in this condition. Thus, a man may be ignorant and may fail to know even that there is such a place as the City of Brotherly Love. But from this it will not follow that he cannot be said to know many things about Philadelphia, including how to get there.
Nor can we reply by saying merely that, because expressions of the