Classic results in computability theory concern extensional results: the behaviour of partial recursive functions rather than the programs computing them. We prove a generalisation of Rice’s Theorem concerning equivalence classes of programs and show how it can be used to study intensional properties such as time and space complexity. While many results that follow from our general theorems can - and have - been proved by more involved, specialised methods, our results are sufficiently simple that little work is needed to apply them.