Routledge Encyclopedia of Philosophy

Immortality in ancient philosophy

New article December 10, 2002

1 Before Plato
2 Plato
3 Aristotle
4 After Aristotle


2 Plato

Plato may be said to have begun from a stock of doctrines on immortality that was largely prepared for him by Socrates’ interest in Pythagorean views of the soul, on one hand and Xenophanean rationalizing of theology on the other. In his earliest depictions of Socrates, Plato makes him espouse an unwavering belief in the existence and immortality of at least some gods and a commitment to the soul’s immortality that is more circumspect and critical but no less profound (Socrates’ apparent agnosticism about the soul’s fate after death in Apology 40c may reflect that dialogue’s emphasis on the avoidance of unjustified claims to knowledge). The idea that the soul is the true locus of personhood, that its welfare is vastly more important than the body’s welfare, that at least some part of it survives death, is judged for its actions and may be reincarnated, that the post-mortem fate of the soul provides reasons to embrace a life of earthly virtue – for all of these Socratic commitments there is Presocratic precedent.

These core commitments are also maintained throughout the Platonic corpus, long after the composition of the Apology and Crito. The use of afterlife judgement as a further incentive to virtue, along with the theory of psychic immortality it entails, may be found in the Gorgias, Meno, Phaedo, Phaedrus, Republic, Theaetetus and Laws. (The Republic’s vindication of the just life in no way depends on eternal rewards, but after that vindication is complete, book X mentions them as an additional consideration.)

What Plato added to these views was not so much new content as a new ambition: to prove the soul’s immortality. The majority of the dialogues attributed to his middle period – especially the Phaedo, Phaedrus and Republic – include explicit attempts at such proofs. The Phaedo is devoted to this task almost single-mindedly and is structured as a series of such proofs. Most critics individuate them as follows.

Opposites Argument 70a–72e. Whatever has an opposite comes to be from its opposite; the cold from the warm, the weaker from the stronger, the sleeping from the waking. Between every pair of opposites there must always be two processes of transformation, e.g. cooling down and warming up, falling asleep and waking up. Living and dead are evidently opposites, and one of the processes between them, namely dying, is evident to us. We may infer that there is a second process by which living things and stuff come from dead things or stuff. This conclusion is taken (by a palpable equivocation on ‘the dead’) to mean that ‘the souls of the dead must be somewhere whence they can come back again’. An appendix argues that if the process from life to death were not matched by a process from death to life, then the original stock of living things would have been exhausted in the infinite past.

Recollection Argument 73a–77e. Our ability to give the right answers in abstract discussions shows that we possess a kind of knowledge (of the Forms, as it happens) that we must have acquired before birth. It follows that ‘our souls existed apart from the body before they took on human form’. That they continue to exist after we die is said to follow by combining this proof with the Opposites Argument outlined above. (On this and the related argument of Plato’s Meno 81 ff. see Innateness in ancient philosophy.)

Resemblance Argument 78b–84b Forms and particulars differ systematically: Forms are invisible, unchanging, uniform and eternal, where particulars are visible, changeable, composite and perishable. The human soul is invisible too, and it investigates Forms without the aid of bodily senses. By ruling a particular body it resembles the divine which rules and leads. Thus the soul is ‘most like the divine, deathless, intelligible, uniform, and indissoluble’. Its uniformity and partlessness exempt it from the decomposition that destroys compounded bodies; for all these reasons we may conclude that it is immortal. (Significantly, it is never claimed that the soul actually is a Form, and the theory of soul-construction in the Timaeus 35 explicitly makes souls a third class of entities distinct from Forms and bodies.)

These three arguments are met by two fascinating and devastating objections from Socrates’ interlocutors, Simmias and Kebes. It is in response to these objections that Socrates propounds his final proof, which is discussed elsewhere (see Plato §13).

The Phaedrus (245) argues for the soul’s immortality from its essence as a self-mover; what acts as an ultimate source of motion for other things cannot have any beginning, or any end. Republic X (609–10) adds the argument that each thing can be destroyed only by its own proper evils – as iron by rust, wood by rot or fire and so on – and if the agents that make it worse do not destroy it, nothing else will. But what makes the soul worse is vice, and this has no tendency to destroy the soul. Thus nothing can destroy the soul, and it is imperishable.

Republic X (611) also argues that the soul’s immortality precludes its having parts (the Resemblance Argument of the Phaedo had already emphasized the soul’s uniformity and simplicity). Socrates claims that the complex psychology elaborated in the bulk of the Republic applies to the soul only as it is ‘maimed by its association with the body’; in itself, and when not incarnate, the soul is partless. Immortality is also attributed only to the partless, purely rational soul in the Timaeus (69), where the lower parts are called ‘mortal’. On the evidence of these three dialogues, then, it seems that immortality is a property only of our rational souls. But the myth in the Phaedrus (247–257) and the Republic’s Myth of Er tend to suggest that immortal souls still possess irrational parts even when divorced from bodies. This ambivalence over the simplicity or complexity of the discarnate soul became a point of controversy among later Platonists.

A new aspect of divine immortality is introduced in the discussion of eternity in the Timaeus (37e). Time itself is created along with the visible cosmos, so all of the entities that cooperated in its creation – including the Creator – must somehow be outside time altogether. This god’s immortality is not merely a matter of its having a life like our own, extended ad infinitum; for the Creator there is no ‘was’ or ‘will be’, a doctrine that later influenced Augustine’s account of atemporal divinity (see Augustine §8). In contrast, the immortality of souls in general (and thus of the lower, created gods) no longer follows from their intrinsic nature; since they came to be and are of a composite nature, they are intrinsically liable to decomposition and destruction. Their immortality is extrinsically guaranteed by the Creator’s continued concurrence, and their eternity, like that of the cosmos itself, is one-sided, towards the future only, a feature that provoked protests from Aristotle (On the Heavens I 12).

How to cite this article:
BRENNAN, TAD (2002). Immortality in ancient philosophy. In E. Craig (Ed.), Routledge Encyclopedia of Philosophy. London: Routledge. Retrieved January 16, 2022, from

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