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.
The Phaedo is not one of the Socratic Dialogues of Plato; nor, on the other hand, can it be assigned to that later stage of the Platonic writings at which the doctrine of ideas appears to be forgotten. It belongs rather to the intermediate period of the Platonic philosophy, which roughly corresponds to the Phaedrus, Gorgias, Republic, Theaetetus. Without pretending to determine the real time of their composition, the Symposium, Meno, Euthyphro, Apology, Phaedo may be conveniently read by us in this order as illustrative of the life of Socrates. Another chain may be formed of the Meno, Phaedrus, Phaedo, in which the immortality of