In the Principles, Descartes famously claimed that ‘the nature of matter, or body considered in general’ is to be ‘extended in length, breadth and depth’ (AT VIIA 42, CSM I 224). As the wording makes clear, what Descartes is offering here, is a general claim about what it is for something to be a body, rather than a claim about what it is for something to be this or that body in particular. But in a letter to Mesland dated February 1645, Descartes suggested that for something to be this or that body in particular just was to be ‘a determinate part of matter, a part of the quantity of which the universe is composed’ (AT IV 166, CSM III 243). 

Now on this account, it seems that few bodies will last very long. As Descartes himself admitted, with any quantitative change a body undergoes, it will on this account cease to be the same body: ‘if any particle of the matter were changed, we would at once think that the body was no longer quite the same, no longer numerically the same’ (AT IV 166, CSM III 243). The identity of human bodies, undergoing continuous processes of growth and renewal, would seem to be ephemeral.

To block the radical outcome that the human body changes identity with every change in quantity, Descartes suggested to Mesland that the conditions for identity over time are different for human bodies than for other material substances. In particular, he suggested that the human body retains an identity over time in virtue of its union with the same soul. Using the language of Aristotelian hylomorphism, he sometimes put this point by saying that ‘the numerical identity of the body of a man does not depend on its matter, but on its form, which is the soul’ (AT IV 166, CSM 243).

But in spite of the hylomorphic language here, Descartes’s view came under fierce critique from Aristotelian thinkers such as the English philosopher and theologian, John Sergeant. In his Method to Science, Sergeant argued that what grounds the identity of a human body needs to be something intrinsic to that body (Sergeant 1696, 420). But the Cartesian soul is an immaterial substance on its own, distinct from the body. It is hence ruled out as an identifier of the human body. The claim in Descartes that ‘the Numerical Identity springs from his having the same Soul’, in other words, ‘is ‘Unreasonable and ill grounded’, and the question of what grounds the identity over time of the human body thus remains wide open’ (Sergeant 1696, 422). 

Sergeant’s Method to Science was read by one of the most important representatives of the Cartesian philosophy in England, Antoine Le Grand. Le Grand was critical of the Aristotelian tenor of the Method to Science, and had little patience with Sergeant’s defence of substantial forms and prime matter. Even so, he did think that, with regard to human bodily identity over time, Sergeant had posed a genuine challenge for the Cartesians. What grounds the identity of the human body needs to be something intrinsic to that body, which hardly makes the human soul a plausible candidate. In a long Appendix to his Dissertatio de ratione cognoscendi of 1698, Le Grand set himself the task of finding an intrinsic identifier for the human organism.

In doing so, however, Le Grand in a sense treats the question of bodily identity over time not as a metaphysical question, but as a natural philosophical question concerning animal generation. For what recent findings on organic generation teach us, he argued, is that organic bodies come with a material core that remains constant for the entire duration of their lives. It is this constant core, Le Grand believes, that grounds their identity over time. His principal source for this idea was the ‘eminent doctor’, the Irish physician Bernard Connor (on Connor, see Stone 2004). It is to the account of animal generation in Connor’s Evangelium medici of 1697, therefore, that I will now first turn.

Connor on Generation

Following a long tradition, Connor believed that the organs now known as the human ovaries were in fact female testicles, which produced their own kind of seed. In fact, what these female seeds contributed to the process of generation, Connor believed, were the outlines of the future organisms that would develop from them. For each of these seeds, according to Connor, contained the rudiments of an organic body:

 Just as the seed of silkworm or a grain of wheat contain in themselves another silkworm or grain with their seeds, thus every membranous capsule of the female seed contains in itself all the parts of a human body, for long before the intercourse of man and woman all of the stamina and rudiments of our body are formed and ordered in the right way and lie hidden in this prolific liquid (Connor 1697, 96).

The stamina Connor mentions here, are a kind of fibres, which provide a basic sketch of the human organism that will grow from it (on this concept of stamina as fibres, see Ishizuka 2012). In conception, what happens is that the ‘seminal ferment’ of the male enters into the pores of the stamina, which causes them to dilate and expand. It is this process of dilation of expansion, indeed, that leads to the development of a viable foetus:

The generation of all animals (and indeed the development of plants) does not consist in the formation of new Organs or parts. Rather, it only consists in this, that the seminal fermentation of the male causes the stamina that are already delineated in the seed, and which exist in a compact way, to expand, and to become fit to take in more food and to grow more (Connor 1697, 101).

Now according to Connor, one of the advantages of this account of animal generation, is that it also provides the key to the problem of organic identity over time.

For even though the stamina dilate and expand, they do not perish. In the development from seed to foetus, the same stamina remain intact. And as the foetus grows into a baby that will develop into a mature human being, the same set of stamina will continue to dilate (Connor 1697, 143). human beings thus come with a core of stamina that remains constant throughout the whole duration of their lives, and it is the material continuity at this level of stamina, Connor believed, that guarantees the identity over time of our organisms:

 As it is clear that, if perhaps not all, then at least most parts of the stamina of our bodies remain intact from youth to old age, our bodies remain the same for the whole course of our lives (Connor 1697, 147-8).

As we will see, Le Grand will develop a similar position as he draws on Connor to account for organic identity over time in terms of preformed stamina. 

Le Grand on Generation and Identity

Contrary to Connor, Le Grand rejects the concept of female testicles. In the Dissertatio, he follows the work of recent anatomists who had identified the female testicles of tradition as human ovaries (on this identification, see Adelmann 1966, 780-81):

With regard to the appearance and natural fabric of the human body, we follow the famous anatomist Steno, who discovered that what were commonly called the female testicles were ovaries, which Van Horne, Kerckring, and De Graaf and others have made manifest as well in their writings. So that it is commonly maintained nowadays that the foetus is hidden in in these ovaries with all of its parts (Le Grand 1698, 120).

Le Grand’s reading of these authors here is correct, insofar as all of them held that human eggs contain at least the rudiments of organic structures at an early stage. Thus in his account of the human ovum, the Amsterdam physician and anatomist, Theodore Kerckring, describes how he lays open the body of a recently deceased woman, to find in her uterus a roundish mass the size of a cherry. This little globule, Kerckring reasons, cannot be anything but a human ovum in an early stage of development, and he seeks permission from the woman’s husband to subject it to further investigation. And what he finds is that, even in this early stage, the egg already reveals the global structure of a human body:

I find that nature, which is diligent and never idle, has in merely three or four days already moulded some shape in the rudiments of a man, in which the head can be clearly discerned from the mass of the body, and in the head of which you will see as through a fog the marks of its organs (Kerckring 1670, 4).

But even though the ovum in this early stage already contains the rudiments of a viable foetus, Kerckring never went so far as to surmise that these rudiments had been present before the egg had left the ovary. It is not at all clear then, that he would have agreed with Le Grand that the complete human foetus lies hidden in the ovary.

Perhaps when Le Grand wrote that ‘it is commonly maintained nowadays that the foetus is hidden in in these ovaries with all of its parts’, he reading the anatomists cited above through the lens of the Dutch entomologist and anatomist, Jan Swammerdam. In works such as his Historia insectorum and the Miraculum naturae, Swammerdam had speculated that the eggs of animals contain the outlines of their offspring, even before the moment of conception. The reproductive system of the first female member of each animal kind, in this view, would contain the organic outlines of all future members of the species (Swammerdam 1669, part 1: 51-2, and Swammerdam 1672, 22).

Like Swammerdam, Le Grand believed that this idea provided an important key to understanding the transmission of original sin. To the extent that all human bodies had been encased within the ovary of Eve, he argued, they all must have in some way been affected by the sin she committed (Le Grand, 1694, part 1: 272. Also Swammerdam 1672, 22). But if the idea that organic structure predates the moment of conception can be used to account for the transmission of original sin, Le Grand also believed that it could be used to account for bodily identity over time. To do so, he harked back to Connor’s account of primordial stamina. 

In the Dissertatio, Le Grand explained that the structures that lie hidden in the female ovaries are built up out of ‘primordial stamina’ that form a kind of ‘vascular membrane’ (Le Grand 1698, 123, 121). This membrane, he believed, will grow as the result of nourishment, and it is with this growth that the primordial stamina contained in the female ovum step by step develop into a viable foetus. After birth, the same structure of stamina remains intact, even though it will continue to expand:   

That this fibrous membrane that, I maintain, hides in the egg, and of which we say the foetus at first only consists, remains for the whole of its life, I too deem to be probable. And from this it is easy to see how a human body remains the same with regard to all of its primordial matter for the whole of its life (Le Grand 1698, 120-1). 

Indeed, the primordial membrane out of which a human body is first built up, according to le Grand, will ‘eternally last with regard to its inner and essential texture, which surely is not at all impossible’ (Le Grand 1698, 121).  It is the material continuity on the level of these primordial stamina that grounds human bodily identity over time. With this account, Le Grand believed he could do justice to the intuition in Sergeant that bodily identity is grounded within the human body itself, while resorting to nothing more than the most recent findings in human reproductive anatomy.

References 

Adelmann, Howard. Marcello Malpighi and the Evolution of Embryology Ithaca: Cornell University Press, 1966.

Adriaenssen, Han Thomas. ‘Antoine Le Grand on the Identity over Time of the Human Body’. British Journal for the History of Philosophy, forthcoming.

Ishizuka, Hisao. ‘Fibre Body. The Concept of Fibre in Eigtheenth-Century Medicine, c. 1700-40’. Medical History 56 (2012), 562-84.

Kerckring, Theordore. Spicilegium anatomicum. Amsterdam: Frisius, 1670.

Le Grand, Antoine. An entire body of philosophy according to the principles of the famous Renate Des Cartes in three books. London: Samuel Roycroft, 1694.

Le Grand, Antoine. Dissertatio de ratione cognoscendi. London: John Hartley, 1698.

Sergeant, John. The Method to Science. London: W. Redmayne, 1696.

Stone, Gerald. ‘Connor, Bernard’. Oxford Dictionary of National Biography. Oxford: Oxford University Press, 2004. Online edition January 2008.

Swammerdam, Jan. Historia generalis insectorum, ofte Algemeene Verhandeling van de Bloedeloose Dierkens. Utrecht: Meinardus van Dreunen, 1669.

Swammerdam, Jan. Miraculum naturae, sive Uteri muliebris fabrica. Leiden: Severinus, 1672.