Phaedo begins with Cebes to question Socrates about various issues. The first question is raised on behalf of Evenus, a Sophist. Cebes asks on his behalf, "who never before wrote a line of poetry," is now in prison "turning Aesop's fables into verse" and also composing a hymn in honor of Apollo (Phaedo, 60d). Socrates answers that he is doing so in order to satisfy intimations received during his dreams that he should make music (Phaedo, 60d-e). Socrates justifies himself by accrediting this sudden interest to a desire to part from the world having obeyed the divination that he often received while dreaming, that he should make music.
Following this explanation, Socrates tells Phaedo to "bid him farewell from me; say that I would have him come after me if he be a wise man" (Phaedo, 61b). Simmias expresses confusion as to why Evenus ought to follow Socrates to death. Socrates, then, states that, "...he, who has the spirit of philosophy, will be willing to die; but he will not take his own life" (Phaedo, 61c). Cebes then raises his doubts as to why suicide is prohibited. Cebes first asks why the philosopher should not kill himself. Socrates replies that while death is the ideal home of the soul, man, specifically the philosopher, should not commit suicide except when it becomes necessary. He asks, "Why do you say…that a man ought not to take his own life, but that the philosopher will be ready to follow one who is dying?" (Phaedo, 61d).
Following this, a discussion about suicide occurs between Cebes and Socrates, in which the latter succeeds in showing the former that one ought not to hasten towards death through suicide. While the philosopher seeks always to rid himself of the body, and to focus solely on things concerning the soul, to commit suicide is prohibited as man is not sole possessor of his body. As stated in the Phaedo: "the philosopher more than other men frees the soul from association with the body as much as possible" (64e-65a). So body and soul are separate. The philosopher frees himself from the body because the body is an impediment to the attainment of truth. The philosopher acts as such in order that the body will not distract the soul from attaining virtue and knowledge. While the body is incapable of distinctly perceiving truth about anything, the pursuit of truth is the philosopher's task. During the Apology, Socrates says of this task, "God orders me to fulfill the philosopher's mission of searching into myself and other men" (Apology, 28e-29a). Socrates says to Simmias in the Phaedo: "Did you ever reach them with any bodily sense? -- And I speak not of these alone, but of absolute greatness, and health, and strength, and, in short, of the reality or true nature of everything. Is the truth of them ever perceived through the bodily organs? Or rather, is not the nearest approach to the knowledge of their several natures made by him who so orders his intellectual vision as to have the most exact conception of the essence of each thing he considers?" (Phaedo, 65d-e).
The philosopher will then accept that he can come closest to true knowledge in death for he will no longer be distracted by the body. As the philosopher seeks death his entire life, he should greet it kindly and not be discouraged upon its arrival. However, it is impossible to be alive without the existence of the body. Death, then, the separation of body and soul, is the philosopher's ideal. He will have lived his entire life preparing for and hoping for death. Socrates best discusses this in the Apology, no living man, be he a poet, sophist, or even Socrates himself, is capable of really knowing anything, the philosopher will see death as a haven for the soul. In death only, the soul may possibly come to actually gain true knowledge. For: "He who has got rid, as far as he can, of eyes and ears and, so to speak, of the whole body, these being in his opinion distracting elements when they associate with the soul hinder her from acquiring truth and knowledge--who, if not he, is likely to attain to the knowledge of true being?" (Apology, 65e-66a).
However, man should not kill himself. Socrates cites the traditional argument that man ought not to kill himself because he possesses no actual ownership of himself, as he is actually the property of the gods. He says, "I too believe that the gods are our guardians, and that we men are a chattel of theirs" (Phaedo, 62b). To this, Cebes assents. For, the body is the property of the gods, and man would be punished were he to destroy something that he does not truly own. Then, it may be concluded that man should not kill himself because he will be punished by the gods. The philosopher, then, will greet death, but not hasten to its arrival. For, while he has spent his life preparing for and awaiting its arrival, it is not virtuous to bring about its occurrence.
Two points are evident from this discussion. First, that the body and soul are held to be separate entities, and that they may be separated, most thoroughly through death. Secondly, in arguing that one ought not to do harm to the possession of the gods, it may be inferred that Socrates believes in an afterlife. For, where else would the gods seek retribution and inflict punishment on the person who acts immorally by committing suicide than in some afterlife? Indeed the only thing worrying Socrates before his death is his duty to the gods. He is concerned that certain things be taken care of in order to provide for a swift and blessed journey to the underworld. So he has taken to composing music and will later remind Crito to sacrifice a cock to Asclepius, god of medicine and healing (Phaedo, 118a). Socrates believes that though the soul is immortal, man must perform certain actions and live in a certain manner in order to ensure that the gods treat its immortality favorably once he has died.
The argument continues that man's soul is immortal, and thus may be punished in some way by the gods even after the separation of soul and body. In the course of this argument, the notion of the afterlife arises, and Socrates treats it in multiple ways, always seeking to show that the soul is immortal. He does so by first formulating cyclical, recollective, and affinity arguments. However, we must first see what death is. Indeed, the first concept needing clarification in order to speak of an afterlife is the nature of death. It must first be shown that Socrates believes death to be one of two things. The first he discusses in both the Apology and the Phaedo. The second is mentioned only in the Apology. Either, "that the body comes to be separated by itself apart from the soul, and the soul comes to be separated by itself apart from the body" (Phaedo, 64c), or it is the complete dissolution of the soul. Cebes is troubled by the latter. He worries that death might signify the complete annihilation of the soul. Cebes speaks of such a view and the men who hold it: "...they fear that when she [the soul] has left the body her place may be nowhere, and that on the very day of death she may perish and come to an end immediately on her release from the body...dispersing and vanishing away into nothingness in her flight" (Phaedo, 70a).
We have two Socratic critiques of this idea. In the Apology, Socrates shows that if the soul were to scatter into nothingness upon death, this would be a great blessing to man. He says that, if, "...death is a state of nothingness and utter unconsciousness," then it is "an unspeakable gain" (Apology, 40c). Socrates goes on to illustrate this claim by saying that if death is of such a nature, then it resembles and even exceeds the most peaceful, dreamless night of sleep ever passed by man during his life. As most men would be hard pressed to come up with a more serene time in their lives, either awake or asleep, than those nights being untroubled by even dreams, then to be so for eternity would be a true blessing (Apology, 40c-d). However, in the Phaedo, Socrates refutes the idea altogether. He does so by showing that the soul continues to exist after death and is immortal. Socrates also refers to such worries about the dispersal of the soul as being childish (Phaedo, 77d).