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Abstract: The generation of hybrid animals, where a mother and father of two different species produce an animal that is a cross between their species, has been thought to pose a challenge to two important principles of Aristotle’s biology: that all species are fixed, and that the father transmits form to the offspring in generation. This paper argues that hybrid generation in Aristotle’s embryology does not give us grounds to reject either of these two principles, by showing that hybrid animals count as “monstrosities” from Generation of Animals IV, animals who belong to the same species as their fathers despite deviating from the morphology of that species.

This paper was awarded the British Society for the History of Philosophy’s Graduate Essay Prize in 2024.

Abstract: In Generation of Animals 2.5, Aristotle says that “wind-eggs,” unfertilized eggs produced by some female birds or fish without male insemination, possess nutritive soul in potentiality—seemingly contradicting his doctrine of “reproductive hylomorphism,” on which the male provides the form or soul to the new animal being generated and the female provides the matter. This paper argues that when Aristotle’s comments about wind-eggs are placed in the context of his account of oviparous generation, they do not contradict the reproductive hylomorphic doctrine. Aristotle distinguishes between the production of an egg and the subsequent conception of the embryo that develops inside the egg, with eggs functioning as uterus analogues. I argue that this means eggs should be understood as parts of the animal that lays them, which possess potential nutritive soul insofar as they are potentially able to perform a reproductive function for the ensouled egg-layer.

Abstract: One of Aristotle’s methods of embryological research was the observation of chick embryos in eggs, in which eggs are treated as analogous to uteri in order to make inferences about embryos in the uteri of live-bearing animals. This chapter takes up Aristotle’s statement of an egg–uterus analogy in Generation of Animals 3.2 and explores the metaphysical commitments behind it. In particular, it argues that Aristotle thinks of eggs as parts of egg-laying animals because of their functional similarity to the uteri of live-bearing animals.