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What Makes A Person?
Apr 1, 1996

The definition of personhood, and the related questions of how to define the beginning and the end of a human life, are among the most widely discussed issues in bioethics at the present time. The outcome of this discussion is vital to urgent problems such as the moral status of the embryo (its right to life), abortion, IVF (test-tube babies), embryo research, organ transplantation and terminating the life of patients in PVS (Persistent Vegetative Stage). Philosophers and scientists have addressed these issues from different perspectives without, as yet, reaching any generally accepted conclusion.

To begin with, we can agree, as pointed out by Mason and McCall Smith (1984, p.107), that what constitutes the state of being a person, or personhood, is a matter of moral decisions, not of scientific facts. The relevant arguments are therefore primarily based on some moral, philosophical and theological hypotheses. However, even these arguments are informed by the scientific knowledge we have recently obtained about the condition and development of the human embryo. Insofar as the question is a moral one, arguments fall broadly into two groups, those that follow a secular approach, and those that follow a theological approach.

According to the secular approach, the basic condition for being a person is being capable of valuing one’s own existence. And the moral difference between a person and non-person lies in the value that persons can give to their own lives. Through language a person can comment on and declare awareness of awareness or fully developed self-consciousness (ibid. pp.l9, 21). Command of human language is thus offered as the decisive criterion. On this argument, pre-embryos, embryos, fetuses and very young infants are living beings, even living human beings, but they are not human persons. So, morally, we owe them nothing.

In his widely read article ‘A defence for abortion and infanticide’, Tooley (1973) observed that it is important to be very clear about what makes an entity a person, what gives that entity a right to life. He went on to define five necessary properties: 1) the capacity to envisage a future state for oneself, and to have desires about it; 2) the capacity to have a concept of a self; 3) being a self; 4); the capacity for self-consciousness; and 5) self-consciousness. As unborn babies, very young infants and PVS patients do not fulfil these requirements; they would not qualify as human persons. Singer (1993, p.87), in a forceful line on personhood, made a point of comparing human ‘animals’ with non-human animals, arguing that there could be a person who is not a member of our species and, conversely, there could also be members of our species who are not persons.

Those writers who, by contrast, accept the spiritual side of being a human person, have used different arguments to define personhood but, generally, link it with the human embryological state. Keith L. Moore, one of the foremost embryologists of our time, answered the question ‘When does the embryo become human?’ as follows: ‘The scientific answer is that the embryo always had human potential, and no other, from the time of fertilization, because of its human chromosome constitution. Two things are definite: (1) human development begins at fertilization, and (2) the zygote and early embryo are living organisms. My personal view is that the embryo becomes human being during the eighth week when it acquires distinctive human characteristics’ (Moore, 1989, p.72). 

Most of the writers who think that human personhood begins at some stage of embryological development base their view on various theological arguments. Before explaining these arguments it will be useful to give some historical background.

Aristotle (d. 322 BC), considered the first thinker to speak explicitly of human life as beginning in the womb, wrote: ‘the soul is the cause and the first principle of the living body’ (1957 edn. p.4l5b). He suggested that, when first formed, the embryo would have a nutritive or vegetative soul, replaced in due time, as a result of the causal influence of the particular semen’s pneuma, by the sensitive soul. Finally, in the case of a human, the rational soul would emerge to complete the generation of a human offspring. Aristotle associated quickening and differentiation into distinct stages of 40 days for the male and 90 days for the female, and so has been traditionally interpreted as placing the beginning of the individual boy and girl at those times respectively.

Aristotle’s ideas on this subject influenced many philosophers and scientists from prior to Christian times right through to the Middle Ages, notably Thomas Aquinas (d.1274), and for several centuries afterwards. His ideas also shaped the views of philosophers and scientists from the Islamic world and the East. For example, according to Musallam (1990), the method of lbn Sina (Avicenna, d. 1037) consisted of bringing Aristotle’s facts up to date, then re-stating the original Aristotelian arguments on the basis of the new facts.

Aristotle’s concept of the soul as the cause and first principle of the living body is confirmed by all monotheistic religions with little divergence. Despite significant differences on other points, these religions share the concept of life as sacred because given by God, and therefore forbid the termination of an innocent human life after it has been given its soul. However, they differ in their understanding of when this happens and what it means. Christian theology is definite that ‘immediate animation’ or ‘ensoulment’ is the instant at which our humanity is determined, but is uncertain when that instant occurs. Mahoney sums up the Christian theological position on the beginning of a human life as follows: In point of fact, current Roman Catholic teaching on the time of human ensoulment is one of uncertainty. Official Roman Catholic teaching is that we cannot be absolutely certain when animation takes place, or when the conceptus or the fetus is a human person; but it may well be precisely at the moment of conception’ (Mahoney 1984, pp. 6 7-9).

Evidently, in the monotheistic religions, certain topics can only he discussed knowledgeably after clear Divine guidance or Revelation. Without such guidance, human beings simply cannot know when ensoulment takes place. Because this information is not disclosed in the Christian scriptures, there is uncertainty on the subject among Christian authorities.

In the case of Islam, the situation is quite different. The creation of the human individual, fetal development and ensoulment are referred to in several dozen verses of the Qur’an in various contexts (32:8-9, 23:13-14, 71:14, 16:4, 75:37-9, 86:6, 77:20-1, 76:2, 22:5, 96:1-2, 40:67, 39:6, 53:45-6, 35 11, 3:6). Also, in the second source of knowledge after the Qur’an, namely the Hadith, there are a number of sayings of the Prophet, upon him be peace, which specifically address the subject of the embryological stages of a human being and the time of ensoulment.

From these texts, the great majority of Muslim scholars have understood that ensoulment takes place 120 days after conception (al-Nawawi, 1965 edn, p.189). However, when the relevant verses and ahadith are considered more carefully, the time for ensoulment should be put at between 40 and 45 days after implantation (the detailed textual discussion to support this view cannot be given here; see Aksoy, 199-) This means that. 49 or 55 days after conception, a human individual, with all the attendant rights, can be considered to exist, due to ensoulment having taken place.

Aristotle’s argument that ‘the soul is the cause and the first principle of the living body’ should not be dismissed as a religious myth. Something important is lacking in all our reflections on the subject if we take into account only the material existence of living beings. Although life is a continuous process, the physical existence of living beings is finite. If a human is taken as an example, every single cell in a human body has a limited (and programmed) lifespan. Some cells live a couple of hours, others a couple of days, weeks or months. After that they die and are shed. It is now known as incontrovertible fact that, with the exception of certain brain cells, all the cells in a human body are replaced with new cells every two years. Thus, in two years time, as regards my physical and material existence, I will be a completely different being from the one I am today. So, if I murder someone today and am caught after two years, I might say: ‘It was not me who did the crime. It was not exactly ‘this brain’ that planned it, not ‘these feet’ that walked to the scene, not ‘this finger’ which pulled the trigger’. This defence is logical and must be acceptable if I am only a material being. Of course, our current legal systems are not based upon the (false) assumption that a person is a merely physical being and therefore I would be unable deny responsibility on these grounds.

There should be something beyond merely physical existence that makes me me. Parfit (1984, Part 3) has discussed the nature of a person and sought answers to such questions as: What makes a person at two different times one and the same’? and What is necessarily involved in the continued existence of a person over time? He defines two kinds of sameness or identity: qualitative identicalness (or exact alikeness), and numerical identicalness (or one-and-the-sameness). He writes: ‘Two white billiard balls are not numerically but may be qualitatively identical. If I paint one of these balls red, it will cease to be qualitatively identical with itself as it was. But the red ball that I later see and the white ball that I painted red are numerically identical. They are one and the same ball’ (ibid., p.20l). According to Parfit, a person is a separately existing entity, distinct from his brain and body, and his experiences. What makes an individual at two different times one and the same person is psychological connectedness and/or continuity, with the right kind of cause. The psychological connectedness is the holding of particular direct psychological connections. And the psychological continuity is the holding of overlapping chains of strong connectedness. Parfit addresses these and similar matters extensively and intelligently in his Reasons and Persons (ibid.).

All the Divine religions and some philosophers name that which provides the necessary continuity to make a person as soul. According to the authority of religion, a living human being consists of body and soul. Soul cannot manifest its existence without a body, and a body cannot be animate and survive without a soul. They are like glove and hand: just as the glove is an inanimate piece of cloth until the hand enters it, so the body becomes a human person only when the soul enters it. Likewise, just as when the hand is removed, the glove reverts to a piece of cloth, so too the human body ceases to be identifiable as a human person when the soul departs. Aristotle expresses the soul in this famous, graphic image: ‘For if the eye was an animal, then sight would be its soul…. so that when sight leaves it is no longer an eye except homonymously, much as we might say of a dead body that it is our friend; in one sense it is but in a very different sense it is not’ (Aristotle, 1957 edn, p.412b).

In sum: when the body meets with the soul it comes to be a human person, with all the attendant rights, especially the right to life.


  • AKSOY, S. (199-) ‘When does a human individual begin to be?: A philosophical, embryological and theological perspective’. (Unpublished paper)
  • AL -NAWAWI. (1965 edn) Sahih-i Muslim Bi-Sharh-i Nawawi, Kitab al Qadar, vol.16, Matbaa-i Misri. Egypt.
  • ARISTOTLE (1957 edn), On the Soul (De Anima), trans. W.S. Hett. W. Heinemann, London and Cambridge, Mass.
  • MAHONEY, J. (1984) Bio-ethics and Belief Sheed & Ward, London.
  • MASON, J.K.& McCAll. Smith, R.A. (1984) Law and Medical Ethics, Butterworths, London.
  • MOORE, K,L..(1989)Before We Are Born, W. B. Saunders Company, Philadelphia.
  • MUSALLAM, B. (1990) ‘The human embryo in Arabic scientific and religious thought’ in G.R. Dunstan, (ed.) 7 ‘The Human Embryo: Aristotle and the Arabic and European Traditions, University of Exeter Press, Exeter. pp.32-46.
  • PARFIT. D. (1984) Reasons and Persons, Clarendon Press, Oxford.
  • RISPLER-CHAIM, V. (1993) Islamic Medical Ethics in the Twentieth Century, E.J. Brill, Leiden.
  • SINGER, P. (1993) Practical Ethics, Cambridge University Press, Cambridge.
  • TOOLEY, M. (1973) ‘A defence of abortion and infanticide’ in J. Feinberg (ed.) The Problem of Abortion’, Wadsworth Publication Company, California, pp. 51-91.