This paper examines Plato's ideas on cause-effect relations in the Phaedo. It maintains that he sees causes as things (not events, states of affairs or the like), with any information as to how that thing brings about the effect relegated to a strictly secondary status. This is argued to make good sense, so long as we recognise that aition means the "thing responsible" and exploit legal analogies in order to understand what this amounts to. Furthermore, provided that we do not presuppose that we already know what can and what cannot count as a cause, Plato proves to have an attractive case for his principle that all causation is a matter of like causing like. Once we appreciate this, we are a little closer to understanding his more idiosyncratic principle, which although puzzling is ubiquitous in his writings and often invoked as a premise in key arguments, that opposites cannot cause opposites. The last part of the paper turns to formal causes, defending Plato's advocacy of them, and examining their role in the Parmenides' Third Man Argument. The main proposal is that Plato's conception of Forms as causes opens the door to a better version of that argument's "Non-identity" premise than those currently available.