Three related questions please: According to Jewish law,
1. What is the status of the fertilized egg? Conception with life (a fetus), conception without life?
2. If there is conception without life at fertilization, when is there life?
3. When is there a soul?
ES cell therapeutic research: Halachic considerations by Mordechai Halperin, MD
The Jewish Law – Halacha – distinguishes between six stages of human maturation.
The six stages of human status are:
I. Pre-implantation embryo – begins with the fusion of gametes.
II. Embryo – begins at implantation, when no active procedure is required to maintain growth.
III. Fetus – begins on the 41st day after conception, when gross organogenesis is completed and human form is established.
IV. Viable fetus – begins when the fetus becomes viable.
V. “Dislodged” fetus – begins at the start of the second stage of labor.
VI. Neonate – begins at birth, when the newborn acquires full human status.
Man’s creation “in the image of G-d” confers infinite value on every innocent human life and renders its destruction a capital offense. While this absolute inviolability only begins at birth – stage VI – from an early stage of its embryonic development the embryo enjoys a very sacred title to life, to be set aside only under exceptional circumstances.
The in vitro pre-implantation embryo (stage I) is different. The extremely low probability that it will reach the neonatal stage reduces its halachic status; for example, the Sabbath laws are not set aside in order to save its “life.” This means that the pre-implantation embryo does not enjoy the same sacred title to life as an implanted embryo. Nevertheless, as long as the in vitro pre-implantation embryo obtains its implantation potential, its destruction is not essentially different from the deliberate waste of semen. This interdiction is merely the obverse of the biblical precept “be fruitful and multiply”; that is, it implies a prohibition against frustrating the procreative act.
During its first 40 days following conception (stage II), the embryo is considered as “mere water” in the context of the laws of impurity. Some later authorities use this Talmudic source as support for minimizing the embryo’s status during this initial period so that the prohibition against “destruction of potential human life” does not exist during this embryonic stage. However, according to other authorities who do not accept this concept, the Sabbath laws are set aside in order to save an implanted embryo, which means that an embryo does have some human status in contrast to the in vitro pre-implantation embryo.
1. Jewish law does not differentiate between destruction of an in vitro pre-implantation embryo and its use for routine scientific research. Unless done for the purpose of saving life, both are forbidden as long as the embryo's potential for implantation exists.
2. An in vitro embryo that has lost its implantation potential may be kept for research even if the research involves the extraction of cells, which implies ending the embryo’s capacity to develop.
3. It is forbidden to use a viable implanted embryo for research purposes.
4. The creation of any embryo for such research purposes is prohibited. Nevertheless, the creation of in vitro pre-implantation embryos for research should be allowed if it is probable that this research will help to save human life. This includes creating embryos by the cloning technology.
5. There is a clear distinction between the pre-implantation and implanted embryo. However, Jewish law does not recognize the arbitrary 14-day limit or the distinction between embryo and pre-embryo.
In summary: In terms of Jewish Law, life begins only childbirth. The Soul is introduced into the embryo already in the 41st day, see Talmud Bavli Tractate Sanhedrin 91b. The "Sh'at Yetzira" ("Hour of Formation") in the Talmud there means the completion of initial stage of morphogenesis – where the embryo achieves the basic human form (Regarding neuronal activity around that time – see Stiles J. The fundamentals of brain development: Integrating nature and nurture. Cambridge: MA, Harvard University Press; 2008)