Besides Plato, three other important sources exist for the study of Socrates: Aristophanes, Aristotle, and Xenophon.
Since no writings by Socrates himself survive to the modern era, his actual views must be discerned from the sometimes contradictory reports of these four sources.
[6][7] There are also four sources extant in fragmentary states: Aeschines of Sphettus, Antisthenes, Euclid of Megara, and Phaedo of Elis.
[13][14][15] Socrates—who is often credited with turning Western philosophy in a more ethical and political direction and who was put to death by the democracy of Athens in May 399 BC—was Plato's mentor.
Stylometric analysis of Plato's work has led some scholars to classify dialogues as falling approximately into three groups, Early, Middle and Late.
[19][20] One notable example is Charles Kahn who argued that Plato had created his works not in a gradual way, but as a unified philosophical vision, whereby he uses Socratic dialogues, a non-historical genre, to flesh out his views.
[22] Two relevant works pertain to periods in Socrates' life, of which Aeschines could not have had any personal first-hand experiential knowledge.
A break of scholarly impasse in respect to understanding, resulted from Campbell making a stylometric analysis in 1867.
[32] An essay written by Friedrich Schleiermacher in 1815 ("The Worth of Socrates as a Philosopher"), published 1818 (English translation 1833) is considered the most significant and influential toward developing an understanding of the problem.
[35] Early in the 21st century, most of the scholars concerned have settled to agreement instead of argument about the nature of the significance of ancient textual sources in relation to this problem.
All of the other dialogues that Schleiermacher accepted as genuine he considered to be integrally bound together and consistent in their Platonism.
Further, the Sophist–Statesman–Philosopher family makes particularly good sense in this order, as Schleiermacher also maintains that the two dialogues, Symposium and Phaedo, show Socrates as the quintessential philosopher in life (guided by Diotima) and into death, the realm of otherness.