The two principal interlocutors are Simmias and Cebes, the disciples of
Philolaus the Pythagorean philosopher of Thebes. Simmias is described
in the Phaedrus as fonder of an argument than any man living; and
Cebes, although finally persuaded by Socrates, is said to be the most
incredulous of human beings. It is Cebes who at the commencement of
the Dialogue asks why 'suicide is held to be unlawful,' and who
first supplies the doctrine of recollection in confirmation of the
pre-existence of the soul. It is Cebes who urges that the pre-existence
does not necessarily involve the future existence of the soul, as is
shown by the illustration of the weaver and his coat. Simmias, on the
other hand, raises the question about harmony and the lyre, which is
naturally put into the mouth of a Pythagorean disciple. It is Simmias,
too, who first remarks on the uncertainty of human knowledge, and
only at last concedes to the argument such a qualified approval as is
consistent with the feebleness of the human faculties. Cebes is the
deeper and more consecutive thinker, Simmias more superficial and
rhetorical; they are distinguished in much the same manner as Adeimantus
and Glaucon in the Republic.
Other persons, Menexenus, Ctesippus, Lysis, are old friends; Evenus
has been already satirized in the Apology; Aeschines and Epigenes
were present at the trial; Euclid and Terpsion will reappear in the
Introduction to the Theaetetus, Hermogenes has already appeared in
the Cratylus. No inference can fairly be drawn from the absence of
Aristippus, nor from the omission of Xenophon, who at the time of
Socrates' death was in Asia. The mention of Plato's own absence seems
like an expression of sorrow, and may, perhaps, be an indication that
the report of the conversation is not to be taken literally.
The place of the Dialogue in the series is doubtful. The doctrine of
ideas is certainly carried beyond the Socratic point of view; in no
other of the writings of Plato is the theory of them so completely
developed. Whether the belief in immortality can be attributed to
Socrates or not is uncertain; the silence of the Memorabilia, and of the
earlier Dialogues of Plato, is an argument to the contrary. Yet in the
Cyropaedia Xenophon has put language into the mouth of the dying Cyrus
which recalls the Phaedo, and may have been derived from the teaching of
Socrates. It may be fairly urged that the greatest religious interest of
mankind could not have been wholly ignored by one who passed his life in
fulfilling the commands of an oracle, and who recognized a Divine plan
in man and nature. (Xen. Mem.) And the language of the Apology and of
the Crito confirms this view.