The first philosopher to focus intensively on the intellectual problems surrounding the Homeric epics was Zoilus of Amphipolis in the early 4th century BCE. His work "Homeric Questions" does not survive, but it seems that Zoilus enumerated and discussed inconsistencies of plot in Homer. Examples of this are numerous: for example, in "Iliad" 5.576-9 Menelaus kills a minor character, Pylaemenes, in combat; but later, at 13.758-9, he is still alive to witness the death of his son Harpalion. These have been humorously described as points where Homer "nodded off," from which comes the proverbial phrase "Homeric Nod." Aristotle's "Homeric Problems", which does not survive, was probably a response to Zoilus.