  This article proposes the use of temporal logic for an analysis of
instrumentality inspired by the work of G.H. von Wright. The first part of the
article contains the philosophical foundations. We discuss von Wright's general
theory of agency and his account of instrumentality. Moreover, we propose
several refinements to this framework via rigorous definitions of the core
notions involved. In the second part, we develop a logical system called
Temporal Logic of Action and Expectations (TLAE). The logic is inspired by a
fragment of propositional dynamic logic based on indeterministic time. The
system is proven to be weakly complete relative to its given semantics. We then
employ TLAE to formalise and analyse the instrumentality relations defined in
the first part of the paper. Last, we point out philosophical implications and
possible extensions of our work.
