Skip to main content
Ensoulment: When Does Human Life Begin?
Apr 1, 2005

One of the most controversial topics in modern bioethics, science, and philosophy is to try to pinpoint the beginning of an individual human life. The consequences of this discussion are vitally important, as they may help to articulate more adequate arguments on some bioethical issues, like the definition of the moral status of the embryo, abortion, and embryo research.1 Many philosophers and scientists have argued about the definition of personhood and when the beginning of a human individual’s life occurs, however an acceptable explanation has not yet been provided. In this field there is a temptation to ask science to choose between opinions and beliefs, yet these neutralize one another. We thought that the question of when human life begins requires the essential aid of different forms of knowledge. Here we become involved in the juncture between science and religion, which needs to be carefully explored.2 In this article we will therefore try to explore this issue from different perspectives. To begin with, we can agree, as pointed out by Mason and McCall Smith, that what constitutes the state of being a person, or personhood, is a moral decision.3 Most religious traditions hold that what makes one a person is the possession of a soul.4 When the body meets with the soul, what results is a human person, with all the attendant rights, especially the basic right to life. Under the light of these considerations our duty is to search for the exact time of ensoulment, in order to prevent us from terminating the lives of actual “human persons,” namely by abortion or embryo research. The purpose of the present study was therefore to determine when, in the course of normal development, a human being begins to exist.

The availability of embryonic stem (ES) cells isolated from human blastocysts may open novel avenues for medical treatment of otherwise incurable diseases.5 ES cells are pluripotent, apparently able to make any cell, except placental cells, and are also immortal.6 However, the generation of human ES cells requires the destruction of early human embryos. This raises the same ethical questions and conflicts that are often heard when the ethics of abortion are discussed: Most people in the pro-life movement regard an embryo to be a full human person with a soul. It has all of the rights of any citizen-including the right to life. Thus any procedure that injures or kills an embryo is seen as murder. However, most people in the pro-choice movement regard the beginning of human personhood to occur much later in pregnancy. Thus, killing a recently fertilized embryo is not seen as the murder of a human person.7 What is the status of the embryo when it is several days old? Is the embryo alive? Yes, from its beginning the embryo is cellular and it is alive; no one questions this. But, is the embryo human? If we could catch the embryo before it reaches a stage where it is judged as human, we would be able to take the ES cells without any concern. In an earlier paper8 it was argued that human life begins when the newly formed body systems begin to function as a whole, towards the end of the embryonic stage. Seeing that twinning can occur as late as day 14 after conception and that such identical twinning will produce two individuals with different lives, this could be proposed as a pre-embryonic stage, i.e. the stage where the single individual person has not yet been determined. In this respect, The Ethics Committee of the American Fertility Society defines an embryo as distinct from a pre-embryo, based on medical science and legal precedents. According to that report and the Warnock Report, which lay behind the 1990 Human Fertilization and Embryology Act, the pre-embryo stage is considered to last until 14 days after fertilization,4 and the pre-embryo is to be respected, but not accorded absolute protection. Today, on the basis of these reports and subsequent legislation, embryo research is allowed up to 14 days of development, up until the formation of the so-called primitive streak, or the beginning of the nervous system, after which the splitting and the forming of twins is no longer possible.

The Christian tradition on this subject is interesting, but can be read in two ways. In that tradition, abortion at any stage has always been regarded as gravely sinful. However, for many centuries the termination of a pregnancy at an early stage carried lesser penalties than a later one. This was related to the view that the human soul did not enter the embryo until 40 days or so after conception, an understanding that was taken over from Aristotle.9 Thus, most Christians make a distinction between the moral status of the unformed and the formed embryo, and think of the human person in the full sense, coming only with a delayed ensoulment. For other Christians, however, fertilization is the point at which human life begins. 

Human Life (Personhood) May Begin at around the 9th Week of Development

While we were searching for the time of the beginning of a human individual life, we encountered a statement from God about the time of ensoulment (the infusion of a human soul in biological matter) in His last book.10 God says in His book (the Qur’an) that, We made out of the “embryo” bones, and clothed the bones in “muscles’” (23:14). This statement indicates that in the embryonic stage, first bones and then muscles form. This is in accordance with embryological development. First the bones form as cartilage models at the 7th week, and then the muscles develop around them from the somatic mesoderm at the 8th week of development. Then We developed out of it another creature. This next part of the statement (23:14) implies that the bones and muscles result in the formation of “another creature.” This may refer to beginning of the personhood (ensoulment) after the end of the eighth week. At this stage, the embryo has distinctive human characteristics and possesses the primordia of all the internal and external organs and parts, and after the eighth week, the human embryo is called a fetus. After He gave it (the embryo) the most appropriate shape, He gave it a soul and then He gave you hearing and sight. This statement (32:9) supports the statement mentioned above (23:14) in that after the embryo takes shape, the soul is infused into the fetus. This statement also indicates that the special senses of hearing and seeing develop in this order, i.e. after the ensoulment; this too which is consistent with embryological knowledge. The formation of the internal ears occurs before the beginning of the eyes, at about the 10th and 11th weeks of development, respectively. Moreover, it is very meaningful that God calls the fetus “you” after the beginning of personhood (ensoulment) (32:9), while the embryo before ensoulment is called “it” (23:14; 32:9) indicating the status of the embryo as only a “thing” or a cell cluster. 10

We suggest therefore that the beginning of a human person as an individual living organism is when the embryo develops into fetus at around the 9th week of development (after the 57th day) after the bones and muscles form, but before the development of hearing and sight. Only at this point do we have a multicellular organism and not merely a mass of living cells stuck together. The soul requires that there is an individuated matter present and prior to this period, that there did not previously exist an individual human organism. A sperm or ovum that exists independently of the other only has a potentiality for human personhood. An embryo which is merely biological material that contains human DNA also has only a potentiality for being human personhood, which implies that it is not yet an actual person.11 Two things may both have only a potentiality to be something else, but one of the two may be closer to actualizing that potentiality than the other. Thus, it could be contended that the embryo is closer to being an actual human person than the sperm or ovum is.11 Therefore, we can say that the informational capacity of the zygote and the early embryo is not sufficient to direct the development of anything personal, and is not sufficient to constitute a genetically stable subject as a human being.

Josef Seifert treats the human body and the soul as two incomplete substances (dualism) that are each completed in human beings as a compositum.12 This position seems to require that the immortal soul only is infused into material committed to being a human individual, and indeed into a fetus with sufficient cortical development to allow cognitive functions. This view is consistent with our suggestion that the soul is added to the already-existing physical body when the newly formed body parts and systems begin to function as a whole. If the soul takes effect when the biological processes have produced a new human life, neither earlier nor later, then it would follow that ensoulment must occur at the end of the embryonic stage when, with the newly-formed brain acting as the central information-exchange point, the commencement of the functioning of the whole produces a new level of life and enables the processes that lead to personhood to begin. This alternative is compatible not only with the facts of modern medicine but also with the traditional understanding of ensoulment as defended by many Roman Catholic moral theologians, which has its roots in Aristotle. These moral theologians argue that the peculiarly human soul is not incarnated until there is an appropriately organized matter.13 However, some Christians believe that Jesus was a human being from the moment of conception and therefore that every human being must come into existence at the moment of conception.9 But some others believe that the conception of Jesus is an exception. It is believed that the events which occurred during the conception and development of Jesus will be explained by Jesus himself when he returns.

That the embryo cannot be considered an individual human being has implications for debates concerning the morality of the various uses to which embryos can be put; such as morning-after pills, intrauterine devices which are abortifacient by stopping implantation, the disposal of excess embryos formed in the process of invitro fertilization, and embryo research.14 Both in the religious context and without it, abortion is difficult to justify at any stage after conception.8 But where the question of the possible use of surplus laboratory embryos is concerned, the time of ensoulment does matter, and if this does not occur until late in the embryonic stage of development, there seems no reason why the opportunity of using the embryos may not be taken, provided-as also seems to be the ethical conclusion even before the religious aspect is considered8-it is for no purpose less than the relief of human suffering which can not be relieved in any other way.15 If “ensoulment” does not occur, as we have suggested, until the new organism functions as a whole, then a decision not to make use of laboratory embryos for medical purposes would be a grave responsibility.

The Soul May Have an Etheric Body

Science postulates that all matter is composed of atoms; atoms, however, are composed of protons, neutrons, and electrons, and those in turn are composed of still finer components, until we attain ether.16 This ether is a universal connecting medium, filling all space to the furthest limits, penetrating the interstices of the atoms without a break in its continuity. So completely does it fill space that it is sometimes identified with space itself, and the universe is built up in this fluid and moves through a sea of ether.16 The atom, the electrons, and the protons of which it is composed all move in a sea of ether, the very air we breathe, the very bodies we inhabit, all things likewise are moving in this sea of ether, the parent element from which all manifestation has been derived. By a kind of instinct, one feels it to be the home of spiritual existence, and to be the vehicle of both matter and spirit.16 No experimental data can be sufficient to bring us to the recognition of a soul, but there must be a substance that is the basis of personal identity, for without space-occupying substance, there would be no way to account for the soul’s ability to move the body,17 and the idea of personality or a soul after bodily death would be inconceivable.18 It seems possible that the substance of the soul could be ether. The modern concept of science is that ether is the primary form of all substance and that all other forms of matter are merely differentiations of ether; it then seems that the substance of the soul which in this life is linked organically with the body is identical with ether. The etheric (astral) body seems to be a supersensible element in humanity that primarily lives and acts in time, but also works into the dynamics of the life processes in the physical body.16 The soul is likely to work into the physical body of the human directly via only that etheric body.16

The Limbic System Seems to Be Primarily Related to the Soul in the Brain

Humans have always contemplated the question of the anatomical location of the soul. The early concept that the cerebral ventricles harbor the soul began to break down only in the Renaissance.19 During the Renaissance, the controversy crystallized into those individuals who supported the heart (cardiocentric soul) and others who supported the brain (cephalocentric soul) as the abode for this elusive entity.20 The brain seems to be the organ that harbors the soul, since the function of the brain is fundamentally linked to being human. The brain controls almost all the functions of the body and determines its psychological makeup, such as intellect and, in a theological sense, the soul.21 Without the brain, such functioning is not possible, since brain death means the end of human life. Children born with anencephaly can never experience a human life. Human identity, personality, and worth are associated with the functioning of the brain.21 Considering the role of the brain in the maintenance of the dynamic equilibrium of the organism, there are compelling reasons for defining the brain as the organ which harbors the soul.

The limbic system is intimately concerned with emotional expression and with the genesis of emotions. The term “limbic system” is applied to the part of the brain that consists of a rim of cortical tissue around the hilus of the cerebral hemisphere and a group of associated deep structures-the amygdala, the hippocampus, and the septal nuclei.22 One characteristic of the limbic system is the paucity of the connections between it and the neocortex (the cortical tissue of the remaining nonlimbic portions of the hemisphere). It is stated that “the neocortex sits astride the limbic system like a rider on a horse without reins.”22 In fact, one of the characteristics of emotions is that they cannot be turned on and off at will. Since the limbic system is intimately concerned with the genesis of emotions and is critically involved in neuropsychiatric disorders,23 we can attribute the role to the limbic system of being a seat from which the soul can work in the physical body.

The Vomeronasal Organ Seems to Be the Point of Entry for the Soul and the Etheric Body

We thought that while the soul has an etheric component (substance), there must be an open window to the brain for the entrance of the soul with the etheric body. In this respect, the vomeronasal organ (VNO), which is found in the nasal cavity and which has connections with the brain only between the 6th and 13th weeks of human development-a period including the suggested time of ensoulment at the 9th week-seems to be the most appropriate window through which the soul and the etheric body can enter the brain. This suggestion is consistent with statements in the Old Testament (Torah) (Genesis-Bereishith 2:7, 7:22), which state that the life (soul) is infused into the human being through the nose. Actually, the VNO is said to be the place in the body where the nervous system is closest to the external world.22 Axons of VNO cells pass through the tiny foramina in the cribriform plates of the ethmoid bone to enter the brain,24 and to make close connections with the amygdala and limbic system,25,27 the seat of emotional, hormonal, and autonomic control; in short, the seat of the soul.

The vomeronasal organ is a fluid-filled, tubular structure located at the base of the nasal septum that opens into the nasal cavity via a duct at its anterior end.28 It is a chemoreceptive structure with direct axonal connections to the accessory olfactory bulbs in many terrestrial vertebrates.29 Pheromones presumably bind to the vomeronasal organ and exert behavioral or physiologic responses, thereby allowing chemical communication between animals of the same species.29,30 The effects of pheromones are thought to be mediated by signals from the main and accessory olfactory bulbs to the amygdala and hypothalamus.28 The vomeronasal system, which is well developed and functional in adult animals, begins to function before or after birth in these animals.31 The human VNO however, seems to be different from that of animals in that it becomes rudimental before birth.32 The VNO in the human embryo contains bipolar cells similar to the developing vomeronasal sensory neurons of other species, but the structure becomes more simplified later in development,33,39 having no obvious way of communication with the brain. The first appearance of the tubular VNO is in the 6th week of human development.40,41 This is when the human VNO resembles that of primates with functional VNOs.42 An examination of the VNO and adjacent tissues suggested that the VNO may lose receptor cells and corresponding vomeronasal nerves and become a ciliated, pseudostratified epithelium at approximately the 13th week.42,43 These observations indicate that1) all embryonic humans develop a functional vomeronasal organ which is homologous with the VNOs of other mammals between the 6th and 13th weeks of age (a period including the time of ensoulment which occurs at around the 9th week of development),2) the human vomeronasal organ does not degenerate prenatally, but very likely loses the functional components of the vomeronasal complex of other mammals; and3) the remnant of the human VNO persists until birth and beyond.36,42,44 These observations strongly support our hypothesis in that the VNO seems to have its main function only during the intrauterine period in humans, especially during the period of ensoulment. The VNO becomes rudimental before birth in humans while it begins to function before or after birth in animals. This difference seems to be very significant, since animals do not harbor any soul, unlike humans, and their VNO is important only after birth, when it allows them to communicate chemically with other animals of the same species. Although no anatomical connection has been demonstrated in humans, Monti-Bloch et al. deduce a physiological connection with the brain, because stimulus delivery to the VNO pit elicited several systemic responses45,47 such as changes in blood pressure and heart rate, small but significant changes in hormonal levels47 and some changes in mood.48 Functional brain imaging studies also revealed consistent activation of the hypothalamus, amygdala, and cingulate gyrus-related structures during adult human VNO stimulation.45 These findings also support our view in that the VNO is strongly related with the emotional centers that harbor the soul, even in the absence of anatomical connections.


The above considerations make it seem likely that human life (personhood) may begin at around the 9th week of development with a delayed ensoulment, and that the soul has an etheric component. The limbic system seems to be a primary center for the soul, while the soul may enter the brain with an etheric body, possibly through the window of vomeronasal organ, which is functional and has connections with the brain only during the suggested time of ensoulment. Therefore lawmakers, philosophers, scientists and any-one in a related field may consider the beginning of human life in their decisions and procedures as being from the 9th week (after the 57th day) of human development. Before this period, the embryo must be regarded as a cell cluster which is to be respected, but not accorded absolute protection. Our second conclusion is that embryonic stem cells have an enormous promise to benefit mankind-to save lives and cure or treat diseases which generate a very strong moral imperative to explore their potential. Almost all spare embryos in fertility clinics will eventually die, due to operator error or equipment malfunction. Spare embryos are routinely destroyed, by flushing them down a drain, by incinerating them, or by thawing them out and allowing them to die. They might as well have their stem cells extracted so that they can be of some use to humanity. If the above thesis is true, then there is no loss of human persons. What is destroyed in this process is human biological material that has not been infused with a soul. We can therefore explore the potential use of embryos and help people who are now burdened by debilitating diseases. So let us enter into the processes of nature and apply the knowledge so derived to help others, to alleviate pain, and to enhance human well-being.


  1. Aksoy, S., “Personhood: A matter of moral decisions.” Eubios J Asian Int Bioethics, 1997, 7:3-4.
  2. Kurjak, A., “The beginning of human life and its modern scientific assessment.” Clin Perinatol, 2003, 30:27-44.
  3. Mason, J.K., McCall Smith, R.A., Law and Medical Ethics, London: Butterworths; 1984.
  4. Glannon, W., “Tracing the soul: medical decisions at the margins of life.” Christ Bioeth, 2000, 6:49-69.
  5. Waite, L., Nindl, G., “Human embryonic stem cell research: an ethical controversy in the US & Germany.” Biomed Sci Instrum, 2003, 9:567-572.
  6. Smith, A., Embryonic Stem Cells in Stem Cell Biology, Marshak DR. et al. (Eds.) New York: Cold Spring Harbor Laboratory Press; 2001: 2-19.
  7. Heinemann, T., Honnefelder, L., “Principles of ethical decision making regarding embryonic stem cell research in Germany.” Bioethics, 2002, 16:530-543.
  8. Shea, M.C., “Embryonic life and human life.” J Med Ethics, 1985,11:205-209.
  9. Folscheid, D., “The status of the embryo from a Christian point of view.” Ethics Med, 1994, 10:57-59.
  10. Moore, K.L., “A scientist’s interpretation of references to embryology in the Qur’an.” JIMA, 1986, 18:15-16.
  11. Eberl, J.T., “The beginning of personhood: a Thomistic biological analysis.” Bioethics, 2000,14:134-157.
  12. Seifert, J., Leib und Seele, Salzburg: Universitatsverlag Anton Pustet; 1973.
  13. Bedate, C.A., Cefalo, R., C., “The zygote: To be or not to be a person.” J Med Philos, 1989, 14:641-645.
  14. Bole, T.J. 3rd , “Metaphysical accounts of the zygote as a person and the veto power of facts.” J Med Philos, 1989, 14:647-653.
  15. Shea, M.,C., “Ensoulment and IVF embryos.” J Med Ethics, 1987, 13:95-97.
  16. Gonzalez de Posada, F., “Reflections on the ether.” An R Acad Nac Med (Madr) 2001, 118:43-72.
  17. Murphy, N., “Whatever happened to the soul? Theological perspectives on neuroscience and the self.” Ann N Y Acad Sci, 2003, 1001:51-64.
  18. MacDougall, D., “Hypothesis concerning soul substance, together with experimental evidence of the existence of such substance.” American Medicine April, 1907.
  19. Schiller, F., “The cerebral ventricles. From soul to sink.” Arch Neurol, 1997, 54:1158-1162.
  20. Del Maestro, R., F., “Leonardo da Vinci: the search for the soul.” J Neurosurg, 1998, 89:874-887.
  21. Werning, C., “Is abortion murder?” Med Monatsschr Pharm, 1995, 8:251.
  22. Ganong, W.,F., Review of Medical Physiology, Lebanon: Typopress; 1989.
  23. Heimer, L., “A new anatomical framework for neuropsyciatric disorders and drug abuse.” Am J Psychiatry, 2003, 160:1726-1739.
  24. Moore, K., L., Clinically Oriented Anatomy, 2nd Ed. Baltimore: Williams and Wilkins; 1985.
  25. Gottfried, J., A., Deichmann, R., Winston, J.S., Dolan, R.J., “Functional heterogeneity in human olfactory cortex: an event-related functional magnetic resonance imaging study.” J Neurosci, 2002, 22:10819-10828.
  26. Halpern, M., “The organization and function of the vomeronasal system.” Annu Rev Neurosci 1987, 10:325-362.
  27. Meredith, M., “Sensory processing in the main and accessory olfactory system: Comparisons and contrasts.” J Steroid Biochem Mol Biol, 1991, 39:601-614.
  28. Kandel, E.R., Schwartz, J.H., Jessel, T.M., (Eds) Principles of Neural Science, 4th ed. New York: McGraw-Hill; 2000.
  29. Zbar, R.I., Zbar, L.I., Dudley, C., Trott, S.A., Rohrich, R.J., Moss, R.L., “A classification schema for the vomeronasal organ in humans.” Plast Reconstr Surg, 2000, 105:1284-1288.
  30. Meredith, M., “Human vomeronasal organ function: A critical review of best and worst cases.” Chem Senses, 2001, 26:433-445.
  31. Salazar, I., Lombardero, M., Aleman, N., Sanchez Quinteiro, P., “Development of the vomeronasal receptor epithelium and the accessory olfactory bulb in sheep.” Microsc Res Tech, 2003, 61:438-447.
  32. Knecht, M., Witt, M., Abolmaali, N., Huttenbrink, K.B., Hummel, T., “The human vomeronasal organ.” Nervenarzt, 2003, 74:858-862.
  33. Boehm, N., Gasser, B., “Sensory receptor-like cells in the human fetal vomeronasal organ.” Neuroreport, 1993, 4:867–870.
  34. Takami, S., “Recent progress in the neurobiology of the vomeronasal organ.” Microsc Res Tech, 2002,58:228-250.
  35. Trotier, D., Eloit, C., Wassef, M., Talmain, G., Bensimon, J.,L., Doving, K.B., Ferrand, J., “The vomeronasal cavity in adult humans.” Chem Senses, 2000, 25:369-380.
  36. Moran, D.T., Jafek, B.W., Rowley, J.C., “The vomeronasal (Jacobson’s) organ in man: ultrastructure and frequency of occurrence.” J Steroid Biochem Mol Biol, 1991, 39:545-552.
  37. Stensaas, L.J., Lavker, R.M., Monti-Bloch, L., Grosser, B.I., Berliner, D.L., “Ultrastructure of the human vomeronasal organ.” J Steroid Biochem Mol Biol, 1991, 39:553-560.
  38. Meisami, E., Bhatnagar, K.P., “Structure and diversity in mammalian accessory olfactory bulb.” Microsc Res Tech, 1998, 43:476-499.
  39. Chuah, M.I., Zeng, D.R., “Olfactory marker protein is present in olfactory receptor cells of human fetuses.” Neuroscience, 1987, 23:363-370.
  40. Bhatnagar, K.P., Smith, T.D., “The human vomeronasal organ. III. Postnatal development from infancy to the ninth decade.” J Anat, 2001, 199:289-302.
  41. Sherwood, R.J., McLachlan, J.C., Aiton, J.F., Scarborough, J., “The vomeronasal organ in the human embryo, studied by means of three-dimensional computer reconstruction.” J Anat, 1999, 195:413-418.
  42. Smith, T.D., Bhatnagar, K.P., “The human vomeronasal organ. Part II: prenatal development.” J Anat, 2000, 197:421-436.
  43. Witt, M., Georgiewa, B., Knecht, M., Hummel, T., “On the chemosensory nature of the vomeronasal epithelium in adult humans.” Histochem Cell Biol, 2002, 117:493-509.
  44. Johnson, E.W., Eller, P.M., Jafek, B.W., “Calbindin-like immunoreactivity in epithelial cells of the newborn and adult human vomeronasal organ.” Brain Res, 1994, 638:329-333.
  45. Monti-Bloch, L., Jennings-White, C., Berliner, D.L., “The human vomeronasal system.” A review. Ann N Y Acad Sci, 1998, 855:373-389.
  46. Monti-Bloch, L., Grosser, B.I., “Effect of putative pheromones on the electrical activity of the human vomeronasal organ and olfactory epithelium.” J Steroid Biochem Mol Biol, 1991, 39:573-582.
  47. Monti-Bloch, L., Diaz-Sanchez, V., Jennings-White, C., Berliner, D.L., “Modulation of serum testosterone and autonomic function through stimulation of the male human vomeronasal organ (VNO) with pregna-4,20-diene-3,6-dione.” J Steroid Biochem Mol Biol, 1998, 65:237-242.
  48. Grosser, B., I, Monti-Bloch, L., Jennings-White, C., Berliner, D.L., “Behavioral and electrophysiological effects of androstadienone, a human pheromone. Psychoneuroendocrinology, 2000, 25:289-299.