"Plato studied political philosophy."
Translation:Ο Πλάτωνας μελέτησε την πολιτική φιλοσοφία.
I thought the simple past can be used for continual actions in the past as well? At the site Perfect English Grammar, for example, they state (among other uses):
2: We use it with finished actions, states or habits in the past when we know from general knowledge that the time period has finished. This includes when the person we are talking about is dead.