This paper has two parts: In the first part, I give a general survey of the various reasons 17th and 18th century life scientists and metaphysicians endorsed the theory of pre-existence according to which God created all living beings at the creation of the universe, and no living beings are ever naturally generated anew. These reasons generally fall into three categories. The first category is theological. For example, many had the desire to account for how all humans are stained by original sin (we were all there). As another example of a theological motivation, some take the organism as an obvious starting point for a teleological argument for God’s existence, and this staring point is sometimes developed into a full-blown theory of pre-existence. The second category could be thought of as non-theological metaphysical, and paramount here is the desire to deal with the metaphysical problem of individuation. So, for example, Leibniz embraces a version of hylomorphism in order to overcome difficulties with Descartes’ theory of material substance, including the difficulty of how to account for enduring material individuals, and Leibniz’s hylomorphism is closely linked with his embrace of pre-existence. The third category might be termed “biological”, and one example of such a concern is how to explain the organic unity of living beings where the whole seems to ontologically precede the parts. This is frequently translated into a temporal priority of whole to parts, and thus pre-existence is posited. Of course, many natural philosophers of the early modern period embrace pre-existence for more than one reason, but in general, these are the three classes of motivations one might have for embracing the theory.
In the second part of the paper I examine in detail one argument that appears in the work of Malebranche. On the face of it, this argument seems to be a biological one, specifically the biological or organic holism argument mentioned above. But upon closer examination, I shall argue, Malebranche’s reasons for endorsing pre-existence bring together several of the arguments discussed in the first part of the paper. I conclude with some considerations about what we can learn about Malebranche as a natural philosopher from his motivations for holding the pre-existence doctrine of generation.