Ensoulment is a philosophical concept referring to the moment at which a human being gains a soul, whether newly created within a developing fetus or pre-existing and added at a particular stage of development.
The exact gestational age at which ensoulment is believed to happen has been debated: a widely held view, dating from at latest the time of Aristotle, was that the human soul entered the forming body at 40 days (male embryos) or 90 days (female embryos), and quickening was also named an indication of the presence of a soul.
Other views are that ensoulment happens at the moment of conception; when the child takes the first breath after being born; at the formation of the nervous system and brain; at the first brain activity; or when the fetus is able to survive independently of the uterus (viability).
Ancient Greeks 
Among Greek scholars, Aristotle (384 – 322 BC) believed a fetus in early gestation has the soul of a vegetable, then of an animal, and only later became "animated" with a human soul by "ensoulment". For him, ensoulment occurred 40 days after conception for male fetuses and 90 days after conception for female fetuses, the stage at which, it was held, movement is first felt within the womb and pregnancy was certain. This is called epigenesis, which is "the theory that the germ is brought into existence (by successive accretions), and not merely developed, in the process of reproduction," in contrast to theory of preformation, which asserts the "supposed existence of all the parts of an organism in rudimentary form in the egg or the seed;" modern embryology holds this latter view.
Catholic Church 
On 27 November 2010, Pope Benedict XVI spoke that
“from the moment of its conception life must be guarded with the greatest care.” [...] With regard to the embryo in the mother's womb, science itself highlights its autonomy, its capacity for interaction with the mother, the coordination of biological processes, the continuity of development, the growing complexity of the organism.
It is not an accumulation of biological material but rather of a new living being, dynamic and marvelously ordered, a new individual of the human species. This is what Jesus was in Mary’s womb; this is what we all were in our mother’s womb. We may say with Tertullian, an ancient Christian writer: “the one who will be a man is one already” (Apologeticum IX, 8), there is no reason not to consider him a person from conception.
Throughout Christianity's two thousand year history, this same doctrine of condemning all direct abortions has been constantly taught by the Fathers of the Church and by her Pastors and Doctors. Even scientific and philosophical discussions about the precise moment of the infusion of the spiritual soul have never given rise to any hesitation about the moral condemnation of abortion.
While the Church has always condemned abortion, changing beliefs about the moment the embryo gains a human soul have led their stated reasons for such condemnation, and the classification in canon law of the sin of abortion, to change over time.
Historical Development 
From the 12th century, when the West first came to know of Aristotle more than his works on logic, mediaeval declarations by Popes and theologians on ensoulment were based on the Aristotelian hypothesis.
Aristotle's epigenetic view of successive life principles ("souls") in a developing human embryo—first a vegetative and then a sensitive or animal soul, and finally an intellective or human soul, with the higher levels able to carry out the functions also of the lower levels—was the prevailing view among early Christians, including Tertullian, Augustine, and Jerome.[need quotation to verify][need quotation to verify][not in citation given][not in citation given] Lars Østnor says this view was only "presaged" by Augustine, who belongs to a period later than that of early Christianity. According to David Albert Jones, this distinction appeared among Christian writers only in the late fourth and early fifth century, while the earlier writers made no distinction between formed and unformed, a distinction that Saint Basil of Caesarea explicitly rejected.:72-73 While the Hebrew text of the Bible only required a fine for the loss of a fetus, whatever its stage of development, the Greek Septuagint (LXX) translation of the Hebrew text, a pre-Christian translation that the early Christians used, introduced a distinction between a formed and an unformed fetus and treated destruction of the former as murder.:9, 24 It has been commented that "the LXX could easily have been used to distinguish human from non-human fetuses and homicidal from non-homicidal abortions, yet the early Christians, until the time of Augustine in the fifth century, did not do so."
The view of early Christians on the moment of ensoulment is also said to have been not the Aristotelian, but the Pythagorean:
As early as the time of Tertullian in the third century, Christianity had absorbed the Pythagorean Greek view that the soul was infused at the moment of conception. Though this view was confirmed by St. Gregory of Nyssa a century later, it would not be long before it would be rejected in favour of the Septuagintal notion that only a formed fetus possessed a human soul. While Augustine speculated whether "animation" might be present prior to formation, he determined that abortion could only be defined as homicide once formation had occurred. Nevertheless, in common with all early Christian thought, Augustine condemned abortion from conception onward.:40
Through the Latin translations of Averroes's (1126–1198) work beginning in the 12th century the legacy of Aristotle was recovered in the West - Christian philosophers such as Thomas Aquinas (1224–1274) adapted to his view, and because they believed that the early embryo did not have a human soul, they did not necessarily see early abortion as murder, though they condemned abortion.:150
The 1312 Council of Vienne declared that the substance of the rational or intellectual soul is of itself and essentially the form of the human body and affirmed Aquinas's stance on delayed hominization.
In 1588, Pope Sixtus V issued the Bull Effraenatam, which subjected those that carried out abortions at any stage of gestation with automatic excommunication and the punishment by civil authorities applied to murderers; but a mere three years later, finding that the results had not been as positive as was hoped, his successor Pope Gregory XIV limited the excommunication to abortion of a formed fetus.:71-72
In 1679, Pope Innocent XI publicly condemned sixty-five propositions taken chiefly from the writings of Escobar, Suarez and other casuists (mostly Jesuit casuists, who had been heavily attacked by Pascal in his Provincial Letters) as propositiones laxorum moralistarum (propositions of lax moralists) and "at least scandalous and in practice dangerous," and forbade anyone to teach them under penalty of excommunication. The propositions included:
34. It is lawful to procure abortion before ensoulment of the fetus lest a girl, detected as pregnant, be killed or defamed.35. It seems probable that the fetus (as long as it is in the uterus) lacks a rational soul and begins to first have one when it is born; and consequently it must be said that no abortion is homicide.
In the 1869 Bull Apostolicae Sedis, Pius IX rescinded Gregory XIV's not-yet-animated fetus exception and re-enacted the penalty of excommunication for abortions at any stage of pregnancy, which even before that were never seen as merely venial sins. Since then, canon law makes no distinction as regards excommunication between stages of pregnancy at which abortion is performed.
In spite of the difference in ecclesiastical penalties imposed during the period when the theory of delayed ensoulment was accepted as scientific truth, abortion at any stage has always been condemned by the Church and continues to be so. However, in its official declarations, the Catholic Church avoids taking a position on the philosophical question of the moment when a human person begins to be:
This Congregation is aware of the current debates concerning the beginning of human life, concerning the individuality of the human being and concerning the identity of the human person. The Congregation recalls the teachings found in the Declaration on Procured Abortion: "From the time that the ovum is fertilized, a new life is begun which is neither that of the father nor of the mother; it is rather the life of a new human being with his own growth. It would never be made human if it were not human already. To this perpetual evidence ... modern genetic science brings valuable confirmation. It has demonstrated that, from the first instant, the programme is fixed as to what this living being will be: a man, this individual-man with his characteristic aspects already well determined. Right from fertilization is begun the adventure of a human life, and each of its great capacities requires time ... to find its place and to be in a position to act". This teaching remains valid and is further confirmed, if confirmation were needed, by recent findings of human biological science which recognize that in the zygote resulting from fertilization the biological identity of a new human individual is already constituted. Certainly no experimental datum can be in itself sufficient to bring us to the recognition of a spiritual soul; nevertheless, the conclusions of science regarding the human embryo provide a valuable indication for discerning by the use of reason a personal presence at the moment of this first appearance of a human life: how could a human individual not be a human person? The Magisterium has not expressly committed itself to an affirmation of a philosophical nature, but it constantly reaffirms the moral condemnation of any kind of procured abortion. This teaching has not been changed and is unchangeable.
Citing the possibly first-century Didache and the Letter of Barnabas of about the same period, the Epistle to Diognetus and Tertullian, the Catholic Church declares that "since the first century the Church has affirmed the moral evil of every procured abortion. This teaching has not changed and remains unchangeable. Direct abortion, that is to say, abortion willed either as an end or a means, is gravely contrary to the moral law."
Even when the prevailing scientific theory considered that early abortion was the killing of what was not yet a human being, the condemnation of abortion at any stage was sometimes expressed in the form of making it equivalent to homicide. Accordingly, the article on abortion in the Catholic Encyclopedia states:
The early Christians are the first on record as having pronounced abortion to be the murder of human beings, for their public apologists, Athenagoras, Tertullian, and Minutius Felix (Eschbach, "Disp. Phys.", Disp. iii), to refute the slander that a child was slain, and its flesh eaten, by the guests at the Agapæ, appealed to their laws as forbidding all manner of murder, even that of children in the womb. The Fathers of the Church unanimously maintained the same doctrine. In the fourth century the Council of Eliberis decreed that Holy Communion should be refused all the rest of her life, even on her deathbed, to an adulteress who had procured the abortion of her child. The Sixth Ecumenical Council determined for the whole Church that anyone who procured abortion should bear all the punishments inflicted on murderers. In all these teachings and enactments no distinction is made between the earlier and the later stages of gestation. For, though the opinion of Aristotle, or similar speculations, regarding the time when the rational soul is infused into the embryo, were practically accepted for many centuries still it was always held by the Church that he who destroyed what was to be a man was guilty of destroying a human life.
Jewish views on ensoulment have varied. Rabbi David Feldman states that the Talmud discusses the time of ensoulment, but considers the question unanswerable and irrelevant to the abortion question. In recounting a purported conversation in which the rabbi Judah the Prince, who said the soul (neshama) comes into the body when the embryo is already formed, was convinced by Antoninus Pius that it must enter the body at conception, and considered the emperor's view to be supported by Job 10:12, the tractate Sanhedrin of the Talmud mentions two views on the question.
In a variant reading the rabbi's first statement was that the soul entered the body only at birth.
Other passages in the Talmud, such as Yevamot 69a and Nidda 30b have been interpreted as implying that ensoulment may occur only after forty days of gestation. The Talmud passages, whether speaking of ensoulment at conception or only after forty days, place the views of the rabbis within Greco-Roman culture, whose ideas the rabbis then linked with texts of Scripture and endowed with theological significance.
The view of ensoulment at conception harmonizes with general lore among rabbis about conscious activity before birth. However, most of them did not apply the word nefesh, meaning soul or person, to a fetus still in the womb. The latter half of the Second Temple period saw increasing acceptance of the idea of the soul as joining the body at birth and leaving it again at death.
One Jewish view put ensoulment even later than birth, saying that it occurs when the child first answers "Amen".
The rabbis in fact formulated no fully developed theory of the timing or nature of ensoulment. It has been suggested that the reason why they were not more concerned about the exact moment of ensoulment is that Judaism does not believe in strict separation of soul and body.
Abortion is permitted by Judaism and it is legal in Israel. Judaism and abortion
|This section does not cite any references or sources. (January 2011)|
Islam does not traditionally hold that ensoulment occurs at the point of conception. Two passages in the Qur'an describe the fetal development process:
...We created you from dust, then from a drop of fluid, then a clinging form, then a lump of flesh, both shaped and unshaped: We mean to make Our power clear to you. Whatever We choose We cause to remain in the womb for an appointed time, then We bring you forth as infants and then you grow and reach maturity. ... (22:5)
We created man from an essence of clay, then We placed him as a drop of fluid in a safe place, then We made that drop into a clinging form, and We made that form into a lump of flesh, and We made that lump into bones, and We clothed those bones with flesh, and later We made him into other forms—glory be to God, the best of creators! (23:12-14)
Traditional scholarship places the point of ensoulment nearer to the end of this process, naming it as anywhere between 40 and 120 days after conception, making abortion permissible until that point, though increasingly disliked as time passed. Tangentially, the first verses revealed to Muhammad (Qur. 96:1-5) state that God "created man from a clinging form," "clinging form" often translated as "embryo."
Contemporary scholarship, however, is more likely to more strongly restrict or even forbid abortion, on the grounds that modern technology has permitted us to perceive life in the womb earlier than was previously possible. All schools of thought, traditional and modern, make allowances for circumstances threatening the health or life of the mother.
- Embodiment, morality, and medicine, by Lisa Sowle Cahill and Margaret A. Farley
- "BBC - Religion & Ethics - When is the foetus 'alive'?: The stages of foetal development". Retrieved 2009-01-05.
- A companion to bioethics By Helga Kuhse, Peter Singer
- Aristotle, History of Animals, book VII, part III
- Norman M. Ford, When Did I Begin? Conception of the Human Individual in History, Philosophy and Science (Cambridge & New York, Cambridge University Press ISBN 978-0-521-42428-8), p. 28
- "[[Oxford English Dictionary]]". epigenesis. Retrieved 2011-01-31. Wikilink embedded in URL title (help)
- "[[Oxford English Dictionary]]". preformation. Retrieved 2011-01-31. Wikilink embedded in URL title (help)
- For a discussion of the differences between epigenesis and the theory of preformation, see this: Jane Maienschein. "Epigenesis and Preformationism". Stanford Encyclopedia of Philosophy. Retrieved 2011-01-31.
- A.A. Long, Stoic Studies (University of California Press 2001 ISBN 978-0-520-22974-7), p. 237
- Tad Brennan, The Stoic Life (Oxford University Press 2005 ISBN 978-0-19-925626-6), p. 155
- Norman Wentworth DeWitt, Epicurus and His Philosophy (University of Minnesota 1954), p. 201
- David Albert Jones, The Soul of the Embryo (Continuum International 2004 ISBN 978-0-8264-6296-1)
- Roman Catholic Church (1965-12-07). "Gaudium et Spes". n. 51. Retrieved 2011-03-22.
- Pope Benedict XVI (2010-11-27). "Celebration of First Vespers of the First Sunday of Advent for unborn life". Retrieved 2011-03-22. "Watch the video here, and see the pictures here."
- Pope John Paul II (1995-03-25). "Evangelium Vitae". 61. Retrieved 2011-01-31.
- Stem cells, human embryos and ethics: interdisciplinary perspectives: Lars Østnor, Springer 2008
- Ana S. Iltis, Mark J. Cherry, At the Roots of Christian Bioethics (M & M Scrivener Press 2010 ISBN 978-0-9764041-8-7), p. 166
- Encyclopedia of Christian Theology, "Aristotelianism, Christian"
- James Edward McClellan, Harold Dorn, Science and Technology in World History (Johns Hopkins University Press 2006 ISBN 0-8018-8360-1), p. 184
- Aquinas notes in Summa Contra Gentiles, lib. 2 cap. 88 n. 3 that "Aristotle teaches in the De generatione animalium [II, 3] [that] the fetus is an animal before becoming a man."
- Dictionary of ethics, theology and society By Paul A. B. Clarke, Andrew Linzey
- When Children Became People: the birth of childhood in early Christianity by Odd Magne Bakke
- Daniel Schiff, Abortion in Judaism (Cambridge University Press 2002 ISBN 978-0-521-52166-6)
- Paul T. Stallsworth, Ruth S. Brown (editors), The Church & Abortion (Abingdon Press 1993 ISBN 978-0-687-07852-3), p. 42
- Summa Theologiae Iª q. 118 a. 2 ad 2. Aquinas's fullest treatment of this is in his De potentia, q. 3 a. 9 ad 9 (Reply to the Ninth Objection).
- Haldane, John; Lee, Patrick (2003). "Aquinas on Human Ensoulment, Abortion and the Value of Life". Philosophy 78: 255–278.
- For a criticism of arguments for "delayed hominization," see also this article by Fr. Benedict Ashley, O.P.
- Decrees of the Council of Vienne
- Encyclopedia of Catholicism
- Nicholas Terpstra, Lost Girls: Sex and Death in Renaissance Florence (Johns Hopkins University Press 2010 ISBN 978-0-8018-9499-2), p. 91
- Jean Reith Schroedel, Is the Fetus a Person? (Cornell University Press 2000 ISBN 978-0-8014-3707-6), p. 19
- Catholic Moral Tradition: "In Christ, a New Creation", David Bohr, Our Sunday Visitor Publishing, 1999, ISBN 0-87973-931-2, p. 293
- Johnstone, Brian V. (March 2005). "Early Abortion: Venial or Mortal Sin?". Irish Theological Quarterly 70 (1): 60. An excerpt can be found here.
- "In the Middle Ages, while the reception of his (Aristotle's) works was a great boon to philosophy, the influence of his scientific works was damaging to science" (Anthony Kenny, Essays on the Aristotelian Tradition (Oxford University Press 2000 ISBN 0-19-825068-1), p. 3).
- The Aristotelian Tradition, p. 3
- Theologians' brief submitted to the House of Lords Select Committee on Stem Cell Research. This document cites many early Christian writers who condemn all forms of abortion. Some of the writers say that a human being begins at conception, thus excluding delayed ensoulment.
- The 2008 declaration Dignitas Personae, which describes abortion as "the deliberate and direct killing, by whatever means it is carried out, of a human being in the initial phase of his or her existence, extending from conception to birth" (Dignitas personae, 23).
- T.L. Frazier, The Early Church and Abortion
- Instruction Donum vitae of the Congregation for the Doctrine of the Faith
- Catechism of the Catholic Church, 2271
- Catholic Encyclopedia, see Abortion
- David Feldman, "Jewish Views on Abortion" in Steven Bayme, Gladys Rosen (editors), The Jewish Family and Jewish Continuity (KTAV 1994 ISBN 978-0-88125-495-2), p. 239
- Avraham Steinberg, "Jewish Perspectives" in Shraga Blazer, Etan Z. Zimmer (editors), The Embryo (Karger 2004 ISBN 978-3-8055-7802-8), p. 34
- Sanhedrin, 11
- Daniel Schiff, Abortion in Judaism (Cambridge University Press 2002 ISBN 978-0-521-52166-6), p. 42, footnote 38
- John D. Loike and Rabbi Moshe Tendler, "Halachic Challenges Emerging From Stem Cell Research" in Jewish Political Studies Review 21:3-4 (Fall 2009)
- Gwynn Kessler, Conceiving Israel (University of Pennsylvania Press 2009 ISBN 978-0-8122-4175-4), pp. 68-69
- Schiff, Abortion in Judaism, p. 43
- Adele Berlin, Maxine Grossman (editors), The Oxford Dictionary of the Jewish Religion (Oxford University Press 2011 ISBN 978-0-19-973004-9), p. 700
- New South Wales Board of Jewish Education, "Judaism and the Body"