Plato 
Lysis, Laches, Ion [EPUB ebook] 

No answer is given in the Lysis to the question, 'What is Friendship?' any more than in the Charmides to the question, 'What is Temperance?' There are several resemblances in the two Dialogues: the same youthfulness and sense of beauty pervades both of them; they are alike rich in the description of Greek life. The question is again raised of the relation of knowledge to virtue and good, which also recurs in the Laches; and Socrates appears again as the elder friend of the two boys, Lysis and Menexenus. In the Charmides, as also in the Laches, he is described as middle-aged; in the Lysis he is advanced in years.