 Much discussion of instrumental rationality has taken place in the context of a debate about whether instrumental rationality is the only kind of practical rationality or, alternatively, there are other requirements of practical rationality as well, such as requirements of prudence and morality.  Typically, the former view is called a “Humean” one and the latter a “Kantian” one. In this section, we’ll consider some possible understandings of the thesis that instrumental rationality is the only kind of practical rationality (§4.1), and whether some version of this thesis is given any support by an instrumental analogue of Lewis Carroll’s famous paradox concerning modus ponens (§4.2).  We’ll also consider the views of Hume (§4.3) and Kant (§4.4) on instrumental rationality. 