In Wittgenstein on Rules and Private Language, Saul Kripke articulates a form of scepticism about meaning. Even though there is considerable disagreement among critics about the reasoning in which the sceptic engages, there is little doubt that he seeks to offer constraints for an adequate account of the facts that constitute the meaningfulness of expressions. Many of the sceptic's remarks concern the nature of the guidance involved in a speaker's meaningful uses of expressions. I propose that we understand those remarks (...) as seeking to give shape to the idea that to use an expression under the guidance of one's understanding is to have a reason for that use, which one's understanding allows one to discern and act on. Any philosophical elucidation of meaning must adequately capture the rational nature of our linguistic acts. (shrink)