Thucydides does not have very many fundamentalist zealots left. Nevertheless many scholars still feel the urge to do away with contradictions and tensions within the text. The urge to resolve them is stronger if inconsistent statements occur in prominent passages which are close to each other, and where the reader is unwilling to posit that the author simply changed his mind between writing them. This paper starts by dealing with a much discussed inconsistency which belongs in this group. I will offer two solutions, a longer one and a shorter one. These solutions will demonstrate that Thucydides uses consistent and recoverable principles. The main aim of the paper however is to show that we should not stop at solutions: interpretive problems can lead to a deeper understanding of Thucydides. The arguments below employ two methodological approaches, one fairly well established and one more novel. By comparing passages exemplifying Thucydides' analysis, and by explaining specific differences between them, we can arrive at some important premises in his ideas on causation and responsibility.