Book excerpt: Rationality requires that we intend the means that we believe are necessary for achieving our ends. Instrumental Rationality explores the formulation and status of this requirement of means-ends coherence. In particular, it is concerned with understanding what means-ends coherence requires of us as believers and agents, and why. Means-ends coherence is a genuine requirement of rationality and cannot be explained away as a myth, confused with a disjunction of requirements to have, or not have, specific attitudes. Nor is means-ends coherence strongly normative, such that we always ought to be means-ends coherent. A promising strategy for assessing why this requirement should exist is to consider the constitutive aim of intention. Just as belief has a constitutive aim (truth) that can explain some of the theoretical requirements of consistency and coherence governing beliefs, intention has a constitutive aim (here called "controlled action") that can explain some of the requirements of consistency and coherence governing intentions. We can therefore better understand means-ends coherence by understanding the constitutive aims of both of the attitudes governed by the requirement, intention, and belief.