© The Author 2016. Published by Oxford University Press, on behalf of the Journal of Medicine and Philosophy Inc. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com The Constitution of the Human Embryo as Substantial Change DAVID ALVARGONZÁLEZ* University of Oviedo, Oviedo, Spain *Address correspondence to: David Alvargonzález, PhD, Universidad de Oviedo, Departamento de Filosofía, Campus de Humanidades, c. Teniente Alfonso Martínez s/n, 33011 Oviedo, España. E-mail: dalvar@uniovi.es This paper analyzes the transformation from the human zygote to the implanted embryo under the prism of substantial change. After a brief introduction, it vindicates the Aristotelian ideas of substance and accident, and those of substantial and accidental change. It then claims that the transformation from the multicelled zygote to the implanted embryo amounts to a substantial change. Pushing further, it contends that this substantial change cannot be explained following patterns of genetic reductionism, emergence, and self- organization, and proposes Gustavo Bueno’s idea of anamorphosis as a means to encapsulate criticism against such positions. Keywords: anamorphosis, blastocyst, morula, pre-embryo, sub- stantial change I. INTRODUCTION At its core, this paper considers the transformation from the human zygote to the implanted embryo to be a substantial change. In Section II, I will introduce the Aristotelian ideas of substance, acci- dent, substantial change, and accidental change and will briefly discuss the scope and limits of their present-day validity. In Section III, I contend that the transformation from the early morula and blastocyst to the implanted embryo amounts to a substantial change, and I develop the idea that indi- vidual human organisms, such as implanted human embryos, are not sub- stances that can be split or divided: somatic indivisibility is deemed to be a feature essential to such organisms, one not yet present in morulas and blastocysts. These two different kinds of individuality (that of the morula and the implanted embryo) strongly imply the existence of two different kinds of substances and, consequently, the occurrence of a substantial change. Journal of Medicine and Philosophy, 41: 172–191, 2016 doi:10.1093/jmp/jhv062 Advance Access publication February 4, 2016 at Universidad Publica de Navarra on September 19, 2016 http://jmp.oxfordjournals.org/ Downloaded from