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Plato’s 19 Proofs of the Immortality of the Human Soul

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William Blake, The Spirit of Plato Unfolds His Worlds to Milton in Contemplation

Is man immortal, or is he not? If he is not, all our disputes are mere amusements, or trials of skill. In this case, truth, reason, religion, which give our discourses such pomp and solemnity, are … mere empty sound, without any meaning in them. But if man is immortal, it will behove him to be very serious about eternal consequences; or, in other words, to be truly religious.
~ Edward Young, Night Thoughts

Art: William Blake, The Spirit of Plato unfolds his Worlds to Milton in Contemplation.

A SpectatorN earlier article proposed the cataloging of Plato’s various proofs for the immortality of the human soul. A fair effort to survey earlier literature has failed to uncover previous systematic attempts; the relative scarcity of studies on this topic generally is unfortunate (and not a little puzzling) given how central the soul’s immortality is for Plato’s philosophy.

As Plato’s proofs are many and subtle we shall proceed incrementally, adding little by little to the present article, until something like a thorough survey is accomplished.

To begin with, some general points.

First, we may in this context distinguish between two kinds of proofs: (1) logical arguments and (2) experiential demonstrations. By an argument we mean a set of propositions or premises, which, by formal rules of logic, imply a definite conclusion; or a set of propositions that together increase the probability that a conclusion is true (i.e., a probabilistic argument.)

By a demonstration we mean an attempt by Plato to bring to our conscious awareness an insight by means other than logical argument. In many cases with Plato this amounts to eliciting an anamnesis (an un-forgetting or recollection) of some previously known or latent knowledge. For example, we previously considered how Plato’s contemplation of the Form of the Good in Symposium 211–212 can be seen as a demonstrative proof of the existence of God. Similarly, some passages of Plato seem intended to evoke in the reader an experiential awareness of the soul’s immortality.

Second, some of Plato’s proofs are more distinct and easy to identify and characterize than others. What may at first seem a single proof may have several variations or senses that merit separate consideration. Here, inasmuch as we are approaching the topic at a data-gathering stage, we will incline more towards separating than aggregating potentially distinct proofs.

Third, some proofs appear in more than one dialogue. Initially we shall be content to, mostly, associate each proof with the dialogue in which it occurs most prominently.

A Bibliography, also to be developed over time, is added. In general the 20th century literature on immortality of the human soul is meager — an indication of the radical materialism that has lately dominated.

One motivation for pursuing the present project is to inform investigation of a related question, namely: have later philosophers introduced many new and original proofs for the immortality of the human soul, or have they, in this area as in many others, more or less only added ‘footnotes’ to Plato? To anticipate somewhat, it is tentatively proposed that one productive way to address this question is to consider three relevant works from different time periods: (1) Book 1 of Cicero’s Tusculan Disputations (which makes frequent reference to Plato’s main work on the soul, Phaedo), (2) Marsilio Ficino’s Platonic Theology (prominently subtitled, On the Immortality of the Soul), and (3) Edward Young’s Night Thoughts (Nights 6 and 7; “Containing The Nature, Proof, and Importance of Immortality.”)

Plato’s Proofs of Immortality

1. Cyclicity argument.

Source: Phaedo 70c–72e.

Summary: All things proceed from their opposites. Just as death proceeds from life, life must proceed from death. Therefore the soul cannot permanently perish.

2. Recollection (or innate knowledge) argument.

Source: Phaedo 72e–77d; cf. e.g., Meno.

Summary: It appears that we know things that we have not learned in this lifetime — as shown by the fact that when they are made salient, we grasp them immediately and they seem already familiar. This suggests to Plato that we have lived before in a pre-existence; and if our souls existed before this life, they will exist after this life.

3. Affinity argument.

Source: Phaedo 78b–84b.

Summary: There are two levels of reality — the temporal and changing, and the Eternal and immutable; the soul has an innate affinity for eternal things (e.g., Platonic Forms; Truth, Beauty and Moral Goodness; mathematical and religious truths); therefore its own nature must be eternal.

4. Form of Life argument.

Source: Phaedo 102b–107b.

Summary: The soul is not only alive itself, but gives life to the body. Therefore it is intimately connected with the essence or Form of Life. Hence it would be illogical or inconsistent for the soul itself to perish.

5. Vitiating principle argument.

Source: Republic 10.608e–611a.

Summary: Every thing has its own principle of destruction, unique to it and innate (e.g., for a body, disease); if a thing is destroyed, it is only by this unique, endogenous principle. The soul has a unique destructive principle, namely vice; yet even the worst vice is not sufficient to completely kill the soul; and since nothing else besides a thing’s internal destructive principle can make it totally perish, the soul must be immortal.

6. Justice argument.

Source: Republic, Book 10 (e.g., 10.612−4, and the Myth of Er that follows).

Unless there are rewards or punishments after this life, it would violate our innate sense of justice. For example, an evil man could avoid punishment for misdeeds by dying. In short, an afterlife of the soul is required to reconcile our strong and innate sense of fairness with the seeming disregard of Fate to moral justice in this life.

7. Simplicity argument.

Source: Republic 611b, Phaedo 78b-d; cf. Plotinus, Enneads 1.1.2, 1.1.9, 1.1.12.

Summary: A thing composed of many elements is susceptible to decomposition; but the soul is a single substance, uncompounded and hence incorruptible.

8. Self-moved mover.

Source: Phaedrus 245c–246a.

Summary: While the soul moves the body, and it moves itself, it is itself not moved by anything external to it. Since being destroyed would imply movement of some sort, the soul, not moved by anything extrinsic, cannot be destroyed and must be imperishable.

9. Universal interest and yearning.

Source: Symposium 201–212.

Diotima’s speeches in Symposium revolve around the subject of immortality. Several senses of immortality are pursued, such as the begetting of children and the imparting of ideas or virtue to other people, leading up to the addressing of immortality in the religious sense. The overall drift is that human beings seem exceptionally interested in immortality and orient much of their lives to striving for it. This would not be logical unless immortality is possible.

10. Proof via purification.

Source: Republic 10.611b–612a; cf. Plotinus Enneads 1.1.12 and especially 4.7.10.

A proof by demonstration. One who is suitably purified, intellectually and morally, may obtain immediate awareness of the soul’s true nature and its immortality.

11. Replenishment argument.

Source: Phaedo 72a-e; cf. Republic 10.611b-d
Summary: Unless the world were not replenished with living souls, eventually all things would be dead; rather, the world is continually replenished with living souls, who must exist somewhere outside of this world before entering. As Socrates puts it, ” if all things that have life should die, and, when they had died, the dead should remain in that condition, is it not inevitable that at last all things would be dead.” (Phaedo 72c). Whether this is merely another statement of, or implicit in, the cyclicity argument is a topic for further consideration.

12. Afterlife testimonies.

Source: Republic Book 10 (Myth of Er).

If we take the Myth of Er literally, then it purports to be an eye-witness account of someone who has personally observed the extra-mundane life of souls. It seems fairly clear that Plato intend us to take the Er myth more than literally; nevertheless, it does serve more or less as an implicit reference by Plato to the genre of survival testimony, of which numerous examples, ancient and modern, exist.

13. Trusted authority.

Source: Meno 81a-b.

Among the Plato’s lesser arguments for the soul’s immortality is an appeal to authority: honored and trustworthy figures of the past have taught it.  The wisest and best of men are the most confident of survival of soul.

14. Tradition and custom.

Source: ?

Widespread or universal tradition implies that belief in immortality is in our common human nature.   This is conceptually different from the proof by trusted authority, though the two clearly go together. (E.g., one function of trusted authority is precisely to articulate most clearly the common knowledge or tradition.) I do not have a definite source for this in the dialogues, but include it here, tentatively, because another source mentioned it in connection with Plato. (Both the tradition and the trusted authority proofs, however, are taken up by Cicero.)

15. Limitless capacity.

Source: ?

Human beings seem to have a limitless capacity for knowledge, which would serve no purpose if the soul did not outlive the body. Here again, I have no definite source for this yet, but the idea is implicit in Plato’s general view of Man’s innate divinity and noetic and moral capabilities; and the Neoplatonist view (derived from Plato) that each human soul contains a copy of all Forms.

16. Example of Socrates.

Source: Apology, Phaedo, Crito.

Socrates’ absolute and unfeigned confidence in the face of death, his nonchalance, and what even approaches an eagerness to shuffle off the mortal coil constitute a demonstrative proof. His actions, that is, testify at least as eloquently as his words to the soul’s immortality.

17. Socrates’ desire to convince others.

Source: Phaedo

Beyond his own confidence in immortality, Socrates is intensely concerned to convince others of it. Such benevolent zeal is indicative of well-founded sincerity and possession of an important truth.

18. Socrates’ sign.

Source: Apology.

One reason Socrates gives for his confidence is that his habitual sign or daemon, which customarily warns him in case of danger, did not oppose him in attending his trial. This, Socrates, fully expecting a death sentence, took as strong evidence that his execution posed no harm. Insofar as Socrates believed his sign, and Socrates is a trusted source, this constitutes evidence for the immortality of the soul. Moreover, insofar as, from the testimony of others, we are persuaded of the sign’s trustworthiness independently of Socrates’ own evaluation of it, that is additional positive evidence for immortality.

19. Conviction of Plato.

Plato also seems intensely concerned with convincing readers of the soul’s immortality. His arguments are clearly presented in a spirit of something more than detached speculation. Cicero puts it well.

Even if Plato gave no reasons for his belief — see how much confidence I have in the man — he would break down my opposition by his authority alone; but he brings forward so many reasons as to make it perfectly obvious that he is not only fully persuaded himself, but desirous of convincing others.
~ Cicero, Tusc. Disp. 1.21.49

Thus Cicero alludes here to two different proofs:  Plato’s authority, and his desire to convince others; and the sheer number or proofs Plato produces is seen as evidence of the latter.


Suggestions are welcome. The goal, however, is not to produce a comprehensive bibliography, but mainly to include works that attempt to consider Plato’s arguments in their totality.

Apolloni, David. Plato’s Affinity Argument for the Immortality of the Soul. Journal of the History of Philosophy, 34(1), 1996, 5–32. (Study of the argument in Phaedo 78b-80d.)

Bett, Richard. Immortality and the Nature of the Soul in the PhaedrusPhronesis, 31(1), 1986, 1–26.

Chase, Thomas. Cicero on the Immortality of the Soul. Cambridge, MA 1851 (repr. 1872).

Connolly, Tim. Plato: Phaedo. Internet Encyclopedia of Philosophy. Web, 13 June 2015. (See also References therein.)

Cornford, Stephen (Ed.). Edward Young: Night Thoughts. Cambridge, 1989 (repr. 2008).

DeGraff, Thelma B. Plato in Cicero. Classical Philology, 35(2), 1940, 143–153.

Elton, Matthew. The Role of the Affinity Argument in the Phaedo. Phronesis, 42(3), 1997, 313–316.

Ficino, Marsilio. Platonic Theology, On the Immortality of the Soul. Michael J. B. Allen (Trans.), James Hankins (Ed.). 6 vols. Cambridge, MA, 2001–2006.

Frede, Dorothea. The Final Proof of the Immortality of the Soul in Plato’s Phaedo 102a–107a. Phronesis, 23(1), 1978, 27–41.

Gallop, David. Plato’s ‘Cyclical Argument’ Recycled. Phronesis, 27, 1982, 207–222.

Gaye, Russell K. The Platonic Conception of Immortality and its Connexion with the Theory of Ideas. Cambridge, 1904 (repr. 2014).

Gertz, Sebastian Ramon Philipp. Death and Immortality in Late Neoplatonism: Studies on the Ancient Commentaries on Plato’s Phaedo. Leiden, 2011.

Geddes, W(illiam) D(uguid). Platonis Phaedo. 2nd ed. London: MacMillan, 1885.

Gilfillan, George (Ed.) Young’s Night Thoughts. Edinburgh, 1853.

Gould, Richard. Cicero’s Indebtedness to the Platonic Dialogues in Tusculan Disputations I. Ph.D. dissertation, Princeton University, 1968.

Hackforth, R. Immortality in Plato’s Symposium. Classical Review, 64(2), 1950, 43–45.

King , J. E. (Trans.) Cicero: Tusculan Disputations. Loeb Classical Library, Cambridge, MA, 1927 (rev. 1945).

MacKenna, Stephen (Trans.), Plotinus: The Enneads. 1st edition. London, 1917. Internet Sacred Text Archive. Web, 16 June 2015.

MacKenna, Stephen (Trans.); Page, B. S. (Ed.), Plotinus: The Enneads. 2nd edition. London, 1956.

O’Brien, Michael J. Becoming Immortal in Plato’s Symposium. In: Douglas E. Gerber (Ed.), Greek Poetry and Philosophy: Studies in Honour of Leonard Woodbury. Chicago, 1984, pp. 185–205.

Patterson, Robert Leet. Plato on Immortality. University Park, PA, 1965.

Peabody, Andrew P. (tr.) Cicero’s Tusculan Disputations. Boston, 1886.

Shorey, Paul. Review of The Platonic Conception of Immortality, and its Connexion with the Theory of Ideas, by R. K. Gaye. Philosophical Review, 14(5), 1905, 590–595.

Shorey, Paul (Tr.). Plato’s Republic. 2 vols. (Loeb Classical Library: Plato in Twelve Volumes, Vols. 5 & 6). Cambridge, MA, 1935 (repr. 1969).

Smith, John. A Discourse Demonstrating the Immortality of the Soul. In: John Smith, Select Discourses, London J. Flesher, 1660; repr. in E. T. Campagnac (ed.), The Cambridge Platonists, Oxford, 1901, pp. 99-157.

Snyder, James G. Marsilio Ficino. The Internet Encyclopedia of Philosophy. Web, 22 June 2015.

Spring, Charles. On the Essence and Immortality of the Soul. London, 1865.

Stanford, Charles S. A Catalogue of Books Treating on the Immortality of the Soul. New York, 1853. (Also appended to: Charles S. Stanford, Phaedo: Or, The Immortality of the Soul, New York, 1854.)

Stuart, Moses. Cicero on the Immortality of the Soul (Questionum Tusculanaram, Liber 1). With Notes and Appendix. Andover, MA, 1833.

Stull, William. Reading the Phaedo in Tusculan Disputations 1. Classical Philology, Vol. 107, No. 1 (January 2012), pp. 38-52.

Uebersax, John S. Plato Divinus: Is Plato a Religious Figure? Web, 15 June 2015.

Westerink, Leendert. G. (Trans.). The Greek Commentaries on Plato’s Phaedo. Vol. 1 (Olympiodorus) & Vol 2 (Damascius). Prometheus Trust, 2009.

Written by John Uebersax

September 8, 2015 at 1:00 am

On Dogmatic Agnosticism

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Many people who call themselves agnostics are arguably dogmatists.  Why do I say this?  Because today atheistic-materialism is a received opinion, a dogma.  And the dominant cultural assumption, as expressed in higher education and mass media, is that Christianity is obsolete, disproven, and all but finished as a paradigm.  Someone like the comedian, Bill Maher, can get on television and make snide jokes about Christians, and imply by innuendo that all Christians are basically stupid bigots, and everyone accepts these statements as completely ordinary, or even ‘cool’.  Nobody expects him to defend his accusations with intelligent arguments.

The problem is that this so-called conclusion is very far from the truth. Christianity has not been refuted or debunked.  Rather, the logical fallacy of ‘demolishing a straw man’ has been committed on a massive scale.  The poorest examples of Christianity (e.g., fundamentalists) are held up as the examples, and these are ridiculed.

The problem is that Christianity is not defined by it’s poorer examples.  In the same way, if we wanted to ridicule democracy as a principle, we could easily find examples where democracy is abused, ridicule those, and thereby conclude that all democracy is bad.  The same principle applies to any ideology or institution.  The simple truth, evident at least since the time of Socrates, is that *most people* are deeply confused.  Christianity is no exception to this rule.  In fact, one could argue that confused people *should* join a religion — since the express purpose of religion is to un-confuse people.  But no religion claims to do that without a long process.  Hence, it is perfectly consistent with the principles of Christianity that, at any given point in time, most Christians are poor Christians!

A true agnosticism would embrace the principle of intellectual humility.  An intellectually humble person doesn’t follow the scenario outlined above. Intellectually humble skeptics or agnostics would recognize their  ignorance as a liability, and therefore make a determined effort to investigate all plausible possibilities that might lead them to a definitive, or at least probable, opinion.

The first prerequisite of such an orientation, therefore, would be to struggle heroically to divest oneself of prejudice — for all people, being inclined to self-interest, habitually distort and select evidence in self-serving ways.  Next, a virtuous skeptic, in the Socratic tradition, would seek out not the worst examples of an opposing viewpoint, but the best.

Here then is my challenge to skeptics or agnostics who want to exert themselves manfully (or womanfully).  I propose that the work of the Roman philosopher, Cicero, titled On Moral Duties (De officiis) expresses, even though it is not an explicitly Christian work, essentially the same religious world view on morality as Christianity does.  What I’m suggesting is that the work is something extraordinary, sublime, beyond the merely rational, or, if you will, inspired.  Cicero’s eclectic synthesis of Platonic, Stoic, and Aristotelian ethics was integrated into Christianity via the later writers such as Ambrose of Milan, St. Augustine, and many others. The spirit of Christian morality is in it.  That is, Cicero’s philosophical writings contain much of what is best in the Christian moral tradition.  Yes, Christianity assimilated it from a non-Christian writer, but this was done, for the most part, in conscious recognition and admiration of Cicero.

Cicero’s work is also extremely interesting and entertaining to read.  It is a literary masterpiece, and ought to be read by everyone.   Nor can I imagine anyone reading without their feeling edified.

That is the proposal I would make to the sincere skeptic or agnostic.  Read this work, and having your mind placed on a higher plane, as reading the work should do, then in that light you will have a more solid and unprejudiced basis for evaluating the plausibility of the Christian tradition.  If the moral principles advocated by Cicero in the work, for example, are laudable and socially constructive, that would be something to factor into an evaluation of the merits and truth of Christianity, which has preserved this moral tradition, and taught it to countless millions of people.

This page has links to several translations of On Moral Duties that can be read online or downloaded.  The Peabody translation is excellent.

Written by John Uebersax

March 29, 2013 at 11:03 pm