Aristotle’s Theory of Aging

Drunken Old Woman. Late 3rd century BCE. Hellenistic Sculpture / Photo by Evergreen State College, Creative Commons

Remarkably little attention has been paid to Aristotle’s theory of aging, or gerontology.

By Adam Woodcox
PhD Student in Philosophy
Rotman Institute of Philosophy
University of Western Ontario


Aristotle was the originator of the scientific study of life and many areas of his biology have received due consideration in recent decades. But remarkably little attention has been paid to his theory of aging, or gerontology1. This lack of attention is remarkable because Aristotle is arguably the first philosopher to show a serious theoretical interest in aging and he has a lot to say about the subject. He considers it a natural process, and so within the purview of his philosophy of nature. On Youth, Old Age, Life and Death, De Iuventute et Senectute (De Iuv.) and On Length and Shortness of Life, De Longitudine et Brevitate Vitae (De Long.) — both of which are almost entirely dedicated to issues related to the phenomenon of aging — together make up over 15 Bekker pages. In addition, many chapters of History of Animals (HA) and Generation of Animals (GA) are dedicated to similar issues.

This paper has two aims. The first is to get clear on the details of Aristotle’s gerontology, piecing together his theory from various remarks made throughout the corpus. I consider Aristotle’s views on why living things age and what makes an organism long-lived (μακρόβιος). Ultimately, I argue that there are two strands in Aristotle’s thinking on the process of aging. The bulk of his discussion addresses the material-efficient causal factors of aging, identified as the growth and decay of the lungs and corresponding exhaustion of heat in the heart. But Aristotle also considers the limits placed on aging by an organism’s formal nature. The second aim of this paper is to show that Aristotle’s gerontology is compatible with and implies (at least some of) his ageism in the social sphere. Specifically, I look at the claim that old age brings about cowardice as a result of the gradual cooling that occurs with age. Accordingly, I show a closer connection than one might expect between Aristotle’s views on aging in the scientific sphere and the social, or between his gerontology and ageism.


De Longitudine / Cornell University Library Digital Collections

Aging is a process that living things undergo2. And life is essentially tied up with soul. Aristotle recognizes many different psychic powers, but he sees the power of nutrition as in some sense the most fundamental since it alone can be separated from the others, while the other powers are always held in conjunction with nutrition (On the Soul 413a 31-32). The nutritive soul is thus the first rung on Aristotle’s scala naturae and common to all living things, both plant and animal. Importantly, this power operates through an internal « vital » heat, so that everything ensouled is said to have heat (θερμότητα, On the Soul 416b 29) or « a natural source of heat » (ἀρχὴν θερμοῦ φυσικήν, Parts of Animals 650a 7), or again « some connate natural heat » (τινὰ σύμφυτον θερμότητα φυσικήν, De Iuv. 469b 6-7). As we will see, this heat plays a central role in Aristotle’s explanation of the process of aging, which is given primarily in two treatises of the Parva Naturalia : De Longitudine et Brevitate Vitae and De Iuventute et Senectute.

De Longitudine introduces a number of problems that any adequate theory of aging must address. The treatise begins with the question of longevity, asking whether there is one cause that makes everything long-lived, or whether the cause is diverse for plants and animals. That there is a single cause is not obvious. We know from the Posterior Analytics that it might be possible for there to be several causes of the same thing (although not for members of the same species). Indeed, in Posterior Analytics longevity is Aristotle’s example of a phenomenon that might admit diverse causal explanations. It might be the case, for instance, that the cause of longevity in quadrupeds is their not having bile, while in birds it is their being dry or something else (99b 4-6).

Generally, a theory of aging ought to account for the fact that some genera are longer-lived than others and also for the fact that some members of a species are longer-lived than others. Specifically, a theory must account for four general « rules of longevity » that are established in Book IV of De Iuventute et Senectute on the basis of observation :

  1. The longest-lived plants enjoy greater longevity than the longest-lived animals3.
  2. Blooded animals live longer than bloodless.
  3. Terrestrial animals live longer than aquatic.
  4. Large animals live longer than small.

When Aristotle turns to consider the reason why these facts hold, we find him appealing to his theory of elements. According to this theory, all animal bodies (and indeed, all sublunary bodies) consist of the hot and the cold, the dry and the wet4. An animal is by nature hot and wet, and in some sense this is what it is to be alive. But old age is dry and cold. Aristotle thinks this is plain to observation, since the living animal is warm and moist, while a corpse is cold and dry (De Long. 466a 17-23). On this picture, the process of aging is tied to the gradual drying up of the internal moisture necessary for life. Aristotle identifies two primary factors that might prolong this drying up : the quantity and the quality of moisture5. A greater quantity is not as easily dried up. And since large and blooded animals contain more moisture, this quantity accounts for rules 2 and 4 (De Long. 466a 25-32). But the quality of moisture is also important. Quality is here understood in terms of warmth or heat, so that moisture will be of greater quality the warmer it is. Since, on the whole, terrestrial animals are warmer than aquatic, the superior quality of moisture accounts for rule 3. This also explains the unusual longevity of humans for their size. For in humans the ratio of qualitative superiority exceeds the quantitative deficiency (De Long. 466b 1 and GA 777a 32-777b 9). The disparity between plants and animals noted in rule 1 is left to the final chapter of De Long., where Aristotle attributes greater longevity to plants due to a certain oiliness and viscosity that helps them retain moisture (De Long. 467a 5-8). In addition, they share with insects the ability to continually renew themselves, generating new branches and roots as the old die off (De Long. 467a 9 sq. and De Iuv. 468b 2 sq).

De Iuventute et Senectute takes a more direct approach to the question of what aging is. The first chapters establish the location of the source of the nutritive soul in the intermediate region of the body and specifically, in blooded animals, the heart. In a sense life is just the participation of the nutritive soul in a body, but this participation is essentially tied up with the maintenance of heat in the heart. If the vital heat is left alone, it will quickly use up all surrounding fuel (i. e. food) and burn itself out, resulting in death. So it must be tempered and cooled, and this occurs primarily through respiration. Working on analogy with a bellows, the lungs draw in air which cools the vital heat before being exhaled (De Iuv. 474a 11-17).

Following an extensive discussion of respiration which includes a survey of alternative views on the subject, Aristotle arrives at something like a definition of old age that ties it to the decay of the lungs:

γένεσις μὲν οὖν ἐστιν πρώτη μέθεξις ἐν τῷ θερμῷ τῆς θρεπτικῆς ψυχῆς, ζωὴ δ μονὴ ταύτης. Νεότης δ‘ ἐστὶν τοῦ πρώτου καταψυκτικοῦ μορίου αὔξησις, γῆρας δ τούτου φθίσις, ἀκμὴ δὲ τὸ τούτων μέσον

generation is the initial participation, mediated by warm substance, in the nutritive soul, and life is the maintenance of this participation. Youth is the period of the growth of the primary organ of refrigeration, old age of its decay, while the intervening time is the prime of life (De Iuv. 479a 29-32, trans. Ross).

The first thing to note about this passage is that Aristotle is again careful to emphasize the relation of the nutritive soul to heat. This association runs throughout De Iuv. and indeed much of Aristotle’s biological writing. He also distinguishes the three stages of life — youth, the prime of life, and old age — with reference to the growth and decay of the primary organ of refrigeration. It is clear from the context of this passage that Aristotle is referring to the lungs6.

Ultimately, old age results in the death of the organism. In all cases death is caused by the destruction of the vital heat. If the cause of destruction is external, the organism undergoes what Aristotle calls a « violent » death. This might happen, for instance, if the heat is overcome by its opposite and so extinguished, as when the organism is cut and an excess of cold introduced into the body, or alternatively if the heat is exhausted and consumes itself as the result of suffocation or starvation. However, if the cause of the destruction of heat is internal and « involved from the beginning in the constitution of the organ », then death is said to be natural (κατὰ φύσιν, De Iuv. 478b 26-27)7. In this case, the heat is exhausted and destroyed by itself rather than its opposite. The lungs are dried up owing to the lapse of time and become hard and earthy. In this state they are incapable of movement and can no longer expand or contract. When the lungs fail, the vital heat is no longer tempered by cooling and is exhausted. Death comes easier in old age since the vital heat is weakened over a lifetime (De Iuv. 479a 15-23).

The bulk of Aristotle’s discussion ties the process of aging to the gradual exhaustion of vital heat and its relation to the heart and lungs. However, he also recognizes the importance of environmental factors on the maintenance of heat and so on the process of aging. The medium in which an animal lives might provide a source of refrigeration, tempering the heat and resulting in a longer life (De Long. 465b 27-29 ; De Iuv. 470b 1-2). Differences in the environment can also account for variation in longevity. Specifically, living in a warmer and airy climate will result in greater longevity than living in a colder and stagnant climate8. Warmer climates are preferable to cold because an organism’s constitution is best maintained by an environment akin to it. A cold climate has a beneficial effect on excess of heat, while a warm environment has a beneficial effect on an excess of cold, for, Aristotle says, « the region reduces to a mean the excess in the bodily condition » (De Iuv. 477b 29-478a 1, trans. Ross). Since we become cold with age, a warm environment will have a beneficial effect on our constitution.

Aristotle uses this framework to explain various features of old age. First, the differences in heat and moisture are reflected in the quantity and appearance of blood, which differ « according to age » (κατὰ τὰς ἡλικίας) : the blood of young animals is fluid and abundant, resembling ichor, but in old age it thickens and becomes scarce9. Second, Aristotle says that the young and the elderly are more likely to produce female offspring, since in the former the heat is not yet perfected (τέλειον) while in the latter it is failing (ἀπολείπει, GA 766b 29-31). The heat of the man in the prime of his life, on the other hand, is perfected, so he is more likely to produce male offspring10. Finally, when Aristotle turns to consider the various differences between kinds of hair in GA V, 3, he uses the same framework to explain the baldness and greying that occur almost exclusively in elderly men (GA 782a 1-785a 5). The skin becomes harder and thicker due to the failing of heat and moisture, so many hairs become disconnected at the base and fall out. In support of this, Aristotle makes the (tenuous) etymological point that the Greek term for old age — τὸ γῆράς — implies that it is earthy — γεηρὸν (GA 783b 5-7). Similarly, the failing heat is unable to properly concoct the nutriment that replenishes the hair, so it begins to decay and lose its colour.

It should be clear at this point that Aristotle views aging in a broadly negative light. Old age is presented as the deterioration of the body and regularly compared to disease. Both old age and illness are due to affections of the body rather than the soul, and specifically drying and cooling of the body (On the Soul 108b 18-29 ; Problems 861a 25-29). He even goes so far as to call disease an « acquired old age » (γῆρας ἐπίκτητον) and old age a natural disease (νόσον φυσικήν, GA 784b 33).


So much for Aristotle’s material-efficient causal account of aging. As we have seen, on this account the length of life is determined in both plants and animals by the maintenance of heat and moisture. In this section, I argue that the quantity and quality of moisture and heat are in turn determined by an organism’s formal nature. Although we might increase longevity, for example, by changing our environment and moving to a warmer climate, for Aristotle we can only do so within a limit determined and set by the nature of the species.

The importance of formal nature to nutrition, and by implication to the process of aging, becomes apparent in On the Soul II, 4. Aristotle there considers the materialist doctrine that identifies fire as the cause of nutrition:

δοκεῖ δέ τισιν τοῦ πυρὸς φύσις ἁπλῶς αἰτία τῆς τροφῆς καὶ τῆς αὐξήσεως εἶναι· καὶ γὰρ αὐτὸ φαίνεται μόνον τῶν σωμάτων [ τῶν στοιχείων] τρεφόμενον καὶ αὐξόμενον, διὸ καὶ ἐν τοῖς φυτοῖς καὶ ἐν τοῖς ζῴοις ὑπολάβοι τις ἂν τοῦτο εἶναι τὸ ἐργαζόμενον

by some the element of fire is held to be the cause of nutrition and growth, for it alone of the bodies or elements is observed to feed and increase itself. Hence the suggestion that in both plants and animals it is it which is the operative force (On the Soul 416a 9-13, trans. Smith).

We might think at first blush that Aristotle is here speaking not of his predecessors or contemporaries, but of the doctrine found in the Parva Naturalia and biological works. For as we have seen, he often speaks of the importance of the vital heat to the operations of nutrition, which include digestion and reproduction. However, he goes on to clarify the sense in which fire might cause nutrition:

τὸ δὲ συναίτιον μέν πώς ἐστιν, οὐ μὴν ἁπλῶς γε αἴτιον, ἀλλὰ μᾶλλον ψυχή· μὲν γὰρ τοῦ πυρὸς αὔξησις εἰς ἄπειρον, ἕως ἂν τὸ καυστόν, τῶν δὲ φύσει συνισταμένων πάντων ἔστι πέρας καὶ λόγος μεγέθους τε καὶ αὐξήσεως· ταῦτα δὲ ψυχῆς, ἀλλοὐ πυρός, καὶ λόγου μᾶλλον ὕλης

a concurrent cause in a sense it certainly is, but not the principal cause : that is rather the soul ; for while the growth of fire goes on without limit so long as there is a supply of fuel, in the case of all complex wholes formed in the course of nature there is a limit or ratio which determines their size and increase, and limit and ratio are marks of soul but not of fire, and belong to the side of account rather than that of matter (On the Soul 416a 13-18, trans. Smith)11.

In this passage, Aristotle clarifies the relation of heat to nutrition. He is careful to distinguish his own account from the materialist alternative which takes fire alone to be the cause of nutrition and growth. The materialist assigns too great a role to fire, which is merely the instrument for the operations of the soul12. There is a certain limit placed on the age of the individual by the nature of the species, and one cannot continue living indefinitely. This limiting influence also explains why members of the same species live to be roughly the same age. But while the nature of the species determines the limit of aging, the species is itself, in a sense, ageless. For although one cannot continue existing as numerically the same individual, he does continue as one in species with his progeny. In this way, we might « partake in the eternal and divine » (On the Soul 415a 29)13.


So far, we have restricted ourselves to Aristotle’s account of aging in the scientific sphere. We have seen that Aristotle has a relatively mature gerontology, addressing the material-efficient cause of aging and the limiting influence of formal nature. I would like in this section to turn to his account of aging in the social sphere, and consider how the two accounts line up. Is the physiology of aging independent from the social reality, or do the two share some connection ? I argue that Aristotle’s views about the character of the elderly are not only consistent with, but are in fact implied by, his commitments in the biological realm. There is thus a close connection between Aristotle’s biology and much of what we might call his ageism in the social sphere.

Aristotle’s characterization of the elderly character is thoroughly negative. This is most obvious in the second book of the Rhetoric when he contrasts the three types of character that accompany the three « ages » of life : (i) the youthful, (ii) the elderly, and (iii) men in their prime14. The elderly character is said to be contrary to the youthful, and both are viewed as extremes while the character of men in their prime is a mean between these, possessing the valuable qualities of both and none of the vices. The elderly are, quite literally, « past their prime » (Rhetoric 1390b 7-9). Many of the vices brought about by old age are the result of the accumulation of negative experiences and interactions with other people. Similarly, many of the vices of youth result from naïveté and inexperience. The young man has not yet been humbled by life, so he is overly optimistic and trustful (to the point of gullibility), living in expectation rather than memory. The elderly character, on the other hand, is pessimistic and cynical. He is distrustful since he has been let down many times ; he covets wealth since he knows how difficult it is to acquire and how easy it is to lose ; and he lacks confidence in the future, because things have so often gone wrong.

Much of this harsh portrait can simply be chalked up to prejudice, whether peculiar to Aristotle or a product of Athenian culture15. However, Aristotle will occasionally identify features of the elderly character that are consistent with and implied by his commitments in the biological realm. So in the Rhetoric, Aristotle says that old age « paves the way » for cowardice. Speaking of the elderly, he makes the following claim:

καὶ δειλοὶ καὶ πάντα προφοβητικοί ἐναντίως γὰρ διάκεινται τοῖς νέοις· κατεψυγμένοι γάρ εἰσιν, οἱ δὲ θερμοί, ὥστε προωδοπεποίηκε τὸ γῆρας τῇ δειλίᾳ· καὶ γὰρ ὁ φόβος κατάψυξίς τίς ἐστιν

they are cowardly, and are always anticipating danger ; unlike that of the young, who are warm-blooded, their temperament is chilly ; old age has paved the way for cowardice ; fear is, in fact, a form of chill (Rhetoric 1389b 29-32, trans. Smith).

This is not an off-hand remark, but in fact reflects Aristotle’s commitment to a deeper view of the relation between body and character. In the Nicomachean Ethics, courage is defined as « a mean with regard to fear and confidence », while cowardice is excessively fearful (1115a 6-7 ; 1115b 34). Moreover, fear is regularly associated with cold, so when one is afraid the upper parts become cold16. Indeed, this is how Aristotle explains heart palpitations near the end of De Iuventute et Senectute. Palpitation (πήδησις), he says, is the rushing together of heat in the heart caused by cooling (διὰ κατάψυξιν, De Iuv. 479b 18). It occurs in people with certain diseases, but also in fear:

καὶ γὰρ οἱ φοβούμενοι καταψύχονται τὰ ἄνω, τὸ δὲ θερμὸν ὑποφεῦγον καὶ συστελλόμενον ποιεῖ τὴν πήδησιν, εἰς μικρὸν συνωθούμενον οὕτως ὥστ’ ἐνίοτ’ ἀποσβέννυσθαι τὰ ζῷα καὶ ἀποθνήσκειν διὰ φόβον καὶ διὰ πάθος νοσηματικόν

for when one is afraid the upper parts become cold, and the hot substance, fleeing away, by its concentration in the heart produces palpitation. It is crushed into so small a space that sometimes life is extinguished, and the animals die of the fright and morbid disturbance (De Iuv. 479b 23-26, trans. Ross).

Old age « paves the way » for cowardice because, as we have seen, there is a gradual cooling of the vital heat over a lifetime, and this cooling makes one more susceptible to fear. Conversely, the young have a hot constitution, so they are less susceptible to fear and as a result more courageous. In this way, the young are in a bodily condition similar to those who are drunk (Rhetoric 1389a 18-28 ; Nicomachean Ethics 1154b 9-10).


This close examination of old age in Aristotle’s work shows that his attitude toward aging in both the scientific sphere and the social is unfavorable. In the scientific sphere, he regularly compares old age to a disease or chronic illness and calls it a failing of the vital heat responsible for life, a deterioration of the body. In the social sphere, he decries the elderly character for a whole host of vicious traits. But it is important to note that aging is not always harmful. For some it is actually beneficial and it can cure us of certain vices. In his discussion of the vice of prodigality, Aristotle says that the prodigal man is « easily cured both by age and by poverty, and thus he may move towards the middle state » (εὐίατός τε γάρ ἐστι καὶ ὑπὸ τῆς ἡλικίας καὶ ὑπὸ τῆς ἀπορίας, καὶ ἐπὶ τὸ μέσον δύναται ἐλθεῖν, Nicomachean Ethics 1121a 20-21, trans. Ross). It is clear how poverty will cure the prodigal man, since he will simply have no wealth to give away. Old age, on the other hand, will cure him because the elderly desire first and foremost what is useful (as opposed to what is noble), and guide their lives by consideration of what is useful. And, of course, wealth is useful. Moreover, experience has taught them how difficult wealth is to obtain and how easy it is to lose, so they are more protective of their wealth and less willing to give it away (Rhetoric 1389b 27-29). And there is no reason to think that the beneficial effects of aging are relevant only to the prodigal man. As we have seen, the gradual cooling of vital heat makes the courageous man into a coward in old age. But if rashness is accompanied by excessive heat, it seems that the cooling of old age can cure the man who in his prime is rash, bringing him toward the mean of courage. So for someone possessing certain vices, aging might bring a cure. However, aging as a degenerative process will likely be a burden to the man who in the prime of his life possesses all the virtues of character.

I hope to have demonstrated that Aristotle has a coherent gerontology which draws on many central features of his philosophy of living nature more generally, including the material-efficient and formal causal factors of biological processes, the role of the heart and lungs in the living organism, and the relation of vital heat to life. While Aristotle’s gerontology is coherent in itself, we have also seen that it is compatible with his ageism in the social sphere. And although aging can in some limited cases have a beneficial effect on certain aspects of natural character, it remains degenerative and deleterious business.


  1. There are, of course, a few exceptions. G. Freudenthal, Aristotle’s Theory of Material Substance, Oxford, Oxford University Press, 1995, and R. A. H. King, Aristotle on Life and Death, London, Duckworth, 2001, both contain excellent discussions of Aristotle’s views on aging, but the subject is usually treated only peripherally or in brief.
  2. That is to say, perishable living things. For Aristotle the celestial bodies are living but do not age, since they consist of a distinct kind of matter. See A. Falcon, Aristotle and the Science of Nature : Unity without Uniformity, Cambridge, Cambridge University Press, 2005.
  3. It is interesting to note that Aristotle’s example of the longest-lived plant is the date-palm (φοῖνιξ, De Iuv. 466a 10). Although date-palms are exceptionally long-lived, living upwards of 150 years, they are certainly not the longest-lived organisms. However, date-palm seeds were discovered during the 1963-1965 excavations of a Herodian fortress in Masada, carbon dated to between 206 a. C. and 24 p. C. In 2005, three of these seeds were planted and one germinated. See S. Sallon, « Germination, Genetics, and Growth of an Ancient Date Seed », Science 320 (2008), p. 1464.
  4. See On the Soul 435a 10-435b 25 for an argument that the body of an animal cannot be simple, i. e. cannot consist of one element.
  5. On the quality of moisture, see in this volume A.-F. Morand, p. 127.
  6. Although I do not address it here, there is a question of how this squares with what Aristotle says elsewhere (especially Parts of Animals 652b 7 sq.) about the important role the brain plays in refrigeration.
  7. Cf. Meteorology 379a 4-6 ; De Iuv. 479a 32-479b 5 ; Physics 230a 30-31.
  8. On the preferability of warm climates to cold, see De Long. 465a 7-10. On the preferability of airy regions to hollow, see Problems 909a 38 sq.
  9. HA 521a 31-521b 3. The relation of blood to character is a recurring theme in Aristotle’s biology. This is explicit in the Parts of Animals, where Aristotle goes so far as to state that « the character of the blood affects both the temperament and the sensory faculties of animals in many ways » (πολλῶν δ’ ἐστὶν αἰτία ἡ τοῦ αἵματος φύσις καὶ κατὰ τὸ ἦθος τοῖς ζῴοις καὶ κατὰ τὴν αἴσθησιν, 651a 12-13, trans. Ogle). For an illuminating discussion of this relation, see M. Leunissen, From Natural Character to Moral Virtue in Aristotle, Oxford, Oxford University Press, 2017.
  10. Of course, this explanation relies on Aristotle’s notorious thesis that the female is in some sense « imperfect » (GA 737a 27-28). For an interesting and extensive study of the subject see R. Mayhew, The Female in Aristotle’s Biology : Reason or Rationalization, Chicago, University of Chicago Press, 2004.
  11. Cf. Parts of Animals 652b 7-15.
  12. For nutrition as a regulative process, see T. K. Johansen, The Powers of Aristotle’s Soul, Oxford, Oxford University Press, 2012.
  13. Cf. GA 731b 31-35 ; On the Soul 415a 26-415b 7. Plato makes a similar point at Symposion 207a-208b.
  14. According to Aristotle, the body is in its prime from thirty to thirty-five, and the mind around forty-nine (Rhetoric 1390b 8-9). This dating has led some scholars to speculate that Aristotle was forty-nine when he wrote the Rhetoric. Others have noted that this dating seems to reflect the Pythagorean view that natural processes of growth are completed in units of seven. Aristotle attributes such a view to certain poets, who « measure life by periods of seven years » and thus identify the prime of intelligence at « about fifty » (Politics 1335b 32-35).
  15. On this point, see F. Woerther, L’Èthos aristotélicien. Genèse d’une notion rhétorique, Paris, Vrin, 2007, p. 255 sq., and especially p. 262 n. 17 for references to prejudice in Sophocles, Euripides, Isocrates, and Demosthenes.
  16. We see the association of cowardice with a cold nature again in Aristotle’s discussion of the cuckoo bird in GA 750a 11-15. Cf. Parts of Animals 650b 27-30. For more on Aristotle’s psycho-physiology, and especially the bodily aspects of thinking, see P. J. van der Ejik, « The Matter of Mind : Aristotle on the Biology of “ Psychic ” Processes and the Bodily Aspects of Thinking », Medicine and Philosophy in Classical Antiquity : Doctors and Philosophers on Nature, Soul, Health, and Disease, Cambridge, Cambridge University Press, 2005, p. 206-237.

Originally published by Cahiers des études anciennes LV (2018, 65-78) under the terms of a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license.