3. Intrinsic criteria

The person being: the embryo becomes a human individual when it becomes a person

The question whether the embryo is a person or not seems to be a clear and simple one. If it is a person, it deserves respect as such. If it were only a ‘pre-embryo’ or a ‘potential person’, it would have less rights. However, the moment when the embryo becomes a person is very much debated. It depends first of all on the vision of man that one takes as a point of departure. In addition, even when there is a single vision of man there can be different ideas about the moment when the human embryo has to be seen as a person.

The criterion of animation

Until the recent past in the Catholic world the discussion about the moment when the human embryo becomes a person was connected with the moment of animation. For that matter, the traditional Christian vision of man, too, defending both direct animation and indirect or delayed animation, did not provide a definitive answer to the question as to when the embryo becomes a person.

The theory of direct animation which implies that the embryo is animated by a human soul from conception onwards has its origin in the writings of Hippocrates. In the view of Hippocrates (460?-370? BC) the embryo was born from the sperm of the father which coagulated in the womb. The blood that was there, not secreted during pregnancy as it is during menstruation, was used by the embryo to nourish itself.[33] The embryo was a human individual from the very beginning and thus had a human soul.

The opposing theory was that of ‘indirect’ or ‘delayed’ animation espoused by Aristotle (384/383-332 BC). In his thought the body of the embryo arose from the menstrual blood retained in the womb during pregnancy. This blood, understood as the material cause of the embryo, in Aristotle’s view, was coagulated by the sperm as an efficient and formal cause, like milk under the influence of fig juice or the curd of cheese.[34] Thus the blood was transformed into the body of the embryo. Through the sperm the menstrual blood received a vegetative soul: ‘thus the physical part, the body, comes from the woman and the soul from the man’.[35] In this way, at the end of the first week, the blood became a living being, comparable to a plant. The vegetative soul was replaced a little time afterwards by a sensitive soul, and this was borne out by the formation of sense organs. This soul was in turn replaced by a rational soul which came from outside and had to have a divine origin.[36] The rational soul could not be present from the outset because its activity required a certain level of development of the organs, especially the sense organs: ‘the soul is, therefore, the first act (perfection) of a body that has a life potentially. The body is such when it possesses organs…If we want to mention something common to every soul, it is that the soul is the first act of natural bodies that possess organs’.[37] On the basis of his observations of aborted embryos, Aristotle concluded that the male embryo was animated by the rational principle of life on the fortieth day and the female embryo on the eightieth day.[38]

The choice between the theory of indirect animation or the theory of direct animation was clearly determined by a difference at the level of the vision of the development of the embryo. Differently from Hippocrates, Aristotle, thinking that the body of the embryo arose from the menstrual blood, could not assume that the embryo was animated starting with conception. His belief that only an organic body could be animated made it unthinkable, in fact, that an amorphous piece of blood contained a human soul as a principle of life. Here Thomas Aquinas followed Aristotle, although not without modifications and additions to Aristotle’s thesis.[39] Until the last century there were still Thomists who supported the theory of delayed animation on the basis of the requisite of what they called a sufficient arrangement of matter to be animated by a rational soul, as is stated in number 15 of the twenty-four Thomist theses published by the Sacred Congregation of Studies on 27 July 1914: ‘On the contrary, the human soul exists on its own and when it can be infused in a subject sufficiently disposed, it is created by God, and by its nature it is incorruptible and immortal’.[40]

In 1827 Karl-Ernst von Baer discovered the ovule in mammals and in man and also the mechanism of fertilisation, as a result of which it was definitively proved that the human body does not begin as a coagulate of blood but as a fertilised ovule. For the majority of theologians this was the reason to believe that animation took place at the moment of conception and not later.[41]

However in order to defend procured abortion, theologians, moralists and ethicists took up the theory of delayed animation again from the 1960s onwards.[42] And given that today researchers have to deal with a fertilised ovule, with an embryo brought about by in vitro fertilisation, the theory of delayed animation also acts to justify experiments on embryos.

To support this theory, on the one hand reliance was placed on an Aristotelian argument according to which animation requires a certain development of the sensorial system: ‘the minimum that we should suppose before admitting the presence of a human soul is the availability of these organs: the senses, the nervous system, the brain and especially the cortex. Given that these organs are not yet mature during the very first stages of pregnancy, I think it is certain that a human person only exists after a few weeks’.[43]

On the other hand, theologians and ethicists often referred – and they still refer – to certain scientific discoveries in the field of embryology that were made last century: 1) the spontaneous loss of fertilised ovules to a notable degree; 2) the formation of monozygotic twins; and 3) the possibility of recombining two or three embryos into a single individual. This paper has already discussed the last two phenomena, but not the first.

On the basis of experimental observations, in the 1920s and 1930s Needham postulated that up to 50% of fertilised ovules were lost spontaneously. For many people this makes it improbable that the fertilised ovule is already animated.[44] This, in fact, would mean that one half of human persons with a soul created directly by God are lost during the first weeks to the first months of pregnancy. For that matter, this objection is not new but goes back to Anselm.[45] In the view of the time it was unthinkable that a conceived human at the very first stages of development was already animated because this would mean that such individuals did not have the possibility of being reconciled with God through baptism. This argument as such, however, is not necessarily in contrast with direct animation. The high mortality rate of children, which until the nineteenth century was around 50%, did not constitute an argument by which to call into question the fact that they were persons.[46]

From the moment when it is animated the embryo becomes a person and thus attains the highest level of a human being. The division of the embryo into twins, which is possible until the formation of the primitive streak at the fourteenth or fifteenth day after conception would, according to the Warnock Report, as we have seen, prove that the embryo during the first stages is not an individual and thus not even a person. The moral philosopher Norman Ford concludes, therefore, that animation can only take place after the formation of the primitive streak.[47] We have observed, however, that the possibility of twinning, or of recombination with other embryos, does not exclude the early embryo being a human individual.

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