The Final Argument for the Immortality of the Soul in Plato’s Phaedo

Bust of Plato, Vatican Museum, Rome, Attribution: Dudva, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

This essay examines whether Plato is indeed guilty of a logical fallacy in his final argument for the immortality of the soul in the Phaedo. If valid, Plato’s argument offers coherent models of the relationships between body and soul (or mind) and the nature of the soul itself. This last issue has intrigued many philosophers, from Plato’s ancient contemporaries to leading thinkers of the modern age. Accordingly, this essay aims not only to promote a clearer understanding of Plato’s position in the Phaedo, but also to address several items of great philosophical interest.

After outlining Plato’s final argument (FA), I will posit that he advocates the notion of the soul as a separable entity that can exist independently of the body. While not perfectly equivalent, this position shares many features with Cartesian substance dualism. After defending FA from the objections of Dorothea Frede and Edwin Hartman, I will go on to show that FA is valid if one accepts Plato’s argument for a type of proto-substance dualism. Finally, I will argue that FA is also sound if and only if one independently accepts the notion that the soul is capable of being alive in the literal sense. To achieve these goals, I will appeal to the arguments of Frede, Hartman, Pakaluk and Weller.

Before formally addressing Plato’s final argument, some preliminary information is necessary. In the Phaedo, Plato first introduces his famous concept of Forms. These are defined as ideal realities, and include such Forms as Beauty itself and Justice itself. Objects detectable by the senses—also known as “sensible objects” — can be described in terms of the Forms in which they participate.[1] The sun (sensible object) is called “bright” and “hot” because it participates in the Forms of Brightness and Heat themselves. Forms are purely objects of knowledge, rather than those of empirical experience. Unlike sensible objects, Forms are invisible to the senses, and can only be detected by the exercise of reason.

For Plato, an object can possess a quality associated with a Form either essentially or accidentally. An essential characteristic is a sine qua non of an object: the object has that property whenever it exists.[2] An example entailed by Plato’s account is that of fire, which participates in the form of Heat itself.[3] Since fire must always be hot, heat is an essential characteristic of fire. An accidental characteristic is any property that does not define the fundamental existence of an object. A red chair has the quality of redness, so participates in Redness itself. If painted green, it would lose its redness, but would still remain a chair.

Plato also argues that, in accordance with their ideal nature, Forms cannot admit their opposites. He extends this to assert that a property in an object will likewise retreat or perish when its opposite approaches.[4] In the case of an object’s accidental characteristics, this can best be understood as a dynamic equilibrium between such opposites. The example used by Plato is that of tallness and shortness: when the tallness in Socrates is approached by shortness, it retreats.[5] It is in this way that he explains the differing heights of Socrates and his interlocutors.

When the characteristic in question is essential, however, such as the heat in fire, Plato expands his theory. He posits that not only will the property in question refuse to admit its opposite, but so will the object to which that character is essential. By this reasoning, fire, and not just its property of heat, would flee or perish at the approach of cold.[6]

Given that objects can be described using their characteristics, it follows that objects possessing essential characteristics can always be described in that way (e.g., “Fire is hot”). By contrast, we must be more specific when discussing accidental properties, saying for example that, “This chair is now green”. It is further entailed that, since such objects refuse to admit the opposites of their essential properties, they can be described in terms of this incapacity. The number three is essentially odd. As such, it refuses to admit the opposite of oddness, being evenness, and can be described as uneven.[7]

It can be plausibly argued that that several of Plato’s key concepts such as Forms and the internal structure of the soul have been revised in his other, debatably subsequent, works. For this reason, I have restricted myself to what can be inferred from the text of the Phaedo itself and secondary sources relating to its contents for my formulations of Plato’s and the underlying assumptions that support them.

With these preliminaries in mind, it is now possible to formalise Plato’s final argument for the immortality of the soul. The final argument (FA) can be summarised as follows:

1. The thing that makes the body alive when present is the soul, so the soul brings life to whatever it occupies.
2. Thus, life is an essential characteristic of the soul.
3. Whatever has an essential characteristic cannot admit that quality’s opposite.
4. Since life is the opposite of death, the soul cannot admit death, and must either flee or perish at its approach. The soul can be described by this incapacity. Accordingly, the soul is deathless.
5. The only way for a soul to “perish” would be to die, accepting death.
6. Since a soul cannot accept death, it must withdraw intact at the approach of death.
7. Thus, the soul cannot perish; it is indestructible.
8. Indestructibility entails immortality.
9. Therefore, the soul is immortal.

Perhaps the first objection that springs to mind is that the inference underlying the move from 1 to 2 is unsupported. Simply because something produces a quality— even if it always does so — does not entail that it possesses that quality itself. A lethal poison can cause death without being dead. This thinking informs the approach taken by Edwin Hartman.[8] Hartman argues that Plato has not separately claimed that the soul possesses life in addition to imparting it, that Plato has merely assumed that it follows from the soul’s essential “bringing along” of life.

In response to Hartman’s objection, Dorothea Frede noted that “bringing along” a given quality was likely not Plato’s only criterion for attributing the essential property of life to the soul. According to Frede, Plato indicates that the only cases under consideration are those where the object in question has an essential character, and does not merely impose this property on something else.[9] This refers back to Plato’s description of objects that essentially possess qualities and hence can always be described in terms of them, which Frede refers to as the “eponymy” criterion.[10] Under this view, the essential “bringing along” of an attribute would merely be considered “a further criterion to distinguish between accidental and essential possession.”[11] This is needed because objects can be described using any of their properties, be they accidental or essential. While it would be circular for Plato to baldly claim that the soul is essentially alive, he can be attributed with the weaker assumption that the soul possesses the character of life. This makes sense of the additional criterion of always “bringing along” the property. When combined, they can be used to form the non-circular syllogism of:

1. What has a property may be described in terms of that property.
2. If something both has a quality and always brings this along to whatever it occupies, then this is an essential characteristic of the object.
3. The soul is both alive and always brings life to whatever it occupies.
4. Therefore, life is an essential characteristic of the soul.

An objection could be based on Plato’s use of fever bringing sickness, which would appear to be an exception to this two-tier model of distinguishing accidental from essential characteristics.[12] Specifically, he argues, “[I]f you ask me what, on coming into a body, makes it sick, I will not say sickness but fever.”[13] The point that he is trying to make here is not that sickness is an essential characteristic of fever. He merely notes that fever is a more sophisticated and useful explanation of a body’s sickness than attributing bodily illness to Sickness itself. On this reading, one need not attribute the character of sickness to fever, despite its transmission of this quality.

While this line of reasoning acquits Plato of circular reasoning on this point, there are still some underlying assumptions that may prove problematic for him. For example, Frede suggests that Plato may be asking too much by assuming that the soul is something that can be “alive” in a literal sense.[14] In justifying this claim, she touches upon an issue debated by various other authors: namely, that Plato equivocates about the nature of the soul.[15] Nevertheless, she acknowledges that his final conclusion in the Phaedo requires that the soul be considered akin to a separable Cartesian substance that can have properties of its own.[16] If this could be reconciled, this would indicate that Plato’s position had much in common with Cartesian substance dualism.

Michael Pakaluk contends that the Phaedo indicates just this view. Like Frede’s argument about the classification of essential characteristics, Pakaluk argues that an earlier passage provides the underlying assumptions for the later arguments.[17] The passage in question, which Pakaluk calls “Socrates’ Defence” (SD), offers a definition of “death” that he claims entails a position of substance dualism.[18] This seems to follow from Plato’s claims that there is such a thing as “death” and that this is nothing “else than the separation of the soul from the body”.[19] Pakaluk notes that some critics think that this definition is circular, requiring that the soul continues to exist apart from the body. This does not follow, however, as Plato does not here assume the soul’s survival upon separation from the body. As Pakaluk correctly notes, “the issue of the soul’s independent existence is distinct from that of its continued existence.” Since it only supports the former, weaker claim, this passage does not indicate that he presupposed the soul’s survival upon separation from the body.[20]

It seems, then, that the purpose of SD is the establish that the soul is distinct from the body. Supporting this claim, Plato considers the kinds of activities in which the soul can be thought to engage independently of the body. After disqualifying the pleasures of food and drink, sex and material possessions as being primarily concerned with the body, he concludes that the soul can pursue the acquisition of knowledge without reference to the body. He further claims that the soul’s connection to the body actually interferes with this project.[21] With this in mind, it seems that Plato has offered a formally valid argument for the soul as a separable substance.

One could object that Plato’s definition of “death” as “the separation of the soul from the body” makes the idea of the living soul fleeing at the approach of death a problematic one. Trading Plato’s familiar use of opposites, life, or perhaps birth, would be the joining of the soul to the body. If this were so, then it would seem that “life” could only be possessed by the conjunction of body and soul. This in turn suggests that “life” could not be realised by the soul alone. Perhaps one could respond to this problem by qualifying Plato’s original definition as only denoting the death of a person, comprising an immaterial substance (the soul) and a material substance (the body). Note that, in this reading, the only death is that of the composite (i.e., the person); either or both of its parts (i.e., the body and the soul) could survive separately.

While this may salvage Plato’s argument, it requires the attribution to Plato of a qualification not explicitly stated in the text. Nevertheless, the Phaedo is set on Socrates’ final day, and SD is the passage where Socrates assures his friends that for him, death need hold no fear. This gives some reason to accept the qualifications that I have suggested. There is, however, another response that is perhaps more compelling. In the context of FA, Plato’s definition could be interpreted as describing the result of death approaching the ensouled body. This would be equivalent to the sense in which a cynical person might say that that marriage was nothing but suffering. In this case, they are not truly claiming that marriage literally is suffering, but that it causes suffering. Under Plato’s model, death’s approach causes the separation of soul from body as the soul flees the opposite of life, its essential characteristic.

I have attempted to present FA in a way that is both clear to the reader and fair to its original formulation. Although I do not claim to have responded to all of the objections to FA, I believe that I have successfully defended it against several of the most powerful challenges to its validity. Hartman’s allegation that Plato conflates the concept of “bringing along” a property with that of possessing it was countered by Frede’s response that FA claims that objects of interest such as the soul must fulfil both criteria. Frede’s concern that Plato equivocated about the nature of the soul was countered by Pakaluk’s assertion that, as an earlier passage (SD) strongly implied substance dualism, this would underlie Plato’s final argument. I then addressed a potential challenge to the validity of FA stemming from Plato’s definition of “death” in SD. If accepted, I believe that my treatment of these objections acquits Plato of fallacy in his final argument, so it can at least be considered formally valid.

I do not, however, claim that FA is without difficulties. Despite its formal validity, concerns remain about the acceptability of its premises. As Frede correctly notes, the final argument’s conclusion requires the acceptance of something akin to substance dualism. Even if one accepts SD as a successful argument for this conclusion, this does not entail that the soul is the kind of substance that can possess “life” as a quality in the literal sense. For example, it is inappropriate to refer to the body, a substance, as “just” or “wise”: in accepting Plato’s proto-substance dualism, one must preclude the body from having the consciousness necessary to realise these virtues. After all, SD suggests that the body merely acts as a distorted filter through which the soul’s consciousness perceives world. With this example in mind, it remains possible that it is similarly inappropriate to consider the soul to be literally alive. As the soul must both possess and bring on life to perform the work required of it in FA, this would pose a genuine problem. It is also important to note that this objection differs substantially from Hartman’s, who asserted that Plato had not separately claimed that the soul possessed life. While formal validity would only require that Plato had claimed that the soul possessed life (Hartman’s concern), soundness would also require that he was correct in making this attribution. As Plato has not made an independent argument for the truth of this notion, whether we can accept his argument hinges upon whether we can independently accept his attribution.

In the final analysis, it would seem that Plato’s final argument for the immortality of the soul in the Phaedo is indeed formally valid; for it to also be sound, and hence, compelling, requires the independent acceptance of the idea that the soul can be “alive” in the literal sense.

I originally wrote this for a university course. I was fortunate enough to win a prize for this essay, which sought to respond to the following question: “Set out and evaluate the final argument for the immortality of the soul in Plato’s dialogue, the Phaedo, taking care to do so with reference to the text”. I have done some light editing (I couldn’t help myself), converting some of the jargon into plan English, but have otherwise reproduced it as it was originally submitted all those years ago.

Endnotes

1. Thomas Mautner (Ed.), The Penguin Dictionary of Philosophy, (England: Penguin Books, 1997), p. 426.
2. Phaedo 103e.
3. Ibid., 103d.
4. Ibid., 102d-e.
5. Ibid., 102e.
6. Ibid., 1026d.
7. Ibid., 1026a-e.
8. Edwin Hartman, “Predication and Immortality in Plato’s Phaedo”, Archiv für Geschichte der Philosophie, 54 (1972), p. 221.
9. Dorothea Frede, “The Final Proof of the Immortality of the Soul in Plato’s Phaedo 102a-107a”, Phronesis, 23 (1978), p. 37. Frede’s comments specifically refer to a passage in the Phaedo (103b-c).
10. Ibid.
11. Ibid., p. 37.
12. Phaedo 105c.
13. Ibid.
14. Frede, “The Final Proof”, p. 38.
15. Frede, “The Final Proof, pp. 38–39; Michael Pakaluk, “Degrees of Separation in the Phaedo”, Phronesis, 48 (2003); Cass Weller, “Fallacies in the Phaedo Again”, Archiv für Geschichte der Philosophie, 77 (1995).
16. Frede, “The Final Proof”, pp. 38–39.
17. Pakaluk, “Degrees of Separation”, p. 90.
18. Pakaluk, “Degrees of Separation”, p. 103. According to Pakaluk, “Socrates’ Defence” runs from 63a3–69e5 of the Phaedo.
19. Phaedo 64c.
20. Pakaluk, “Degrees of Separation”, p. 103.
21. Phaedo 65a-c.