 The notion of practical irrationality at work here seems implicit in the Groundwork. Kant there (1785: 413–418) introduces a principle that Thomas Hill, Jr. calls (1992: 17–37) “the hypothetical imperative”: If you will an end, then you ought to will the means to it that are necessary and in your power, or give up willing the end. Willing an end presumably involves setting it and attempting to realize it. According to Kant, the hypothetical imperative is a principle of reason: all of us are rationally compelled to conform to this principle. An agent would be violating the hypothetical imperative and thus acting irrationally by willing an end yet, at the same time, willing another end, the attainment of which would, he is aware, make it impossible for him to take the otherwise available and necessary means to his original end. An agent would violate the hypothetical imperative, for example, by willing now to buy a house and yet, at the same time, willing to use the money he knows he needs for the down payment to make a gift to his niece. If he willed to make the gift, he would be failing to will the necessary means in his power to buy the house. The Kantian hypothetical imperative implies that it is irrational to will to be thwarted in attaining ends that one is pursuing. In typical cases, if a promisee willed the end of a false promisor, she would be doing just that.