Does life begin only when the embryo implants?

Photo copyrighted. Courtesy of Films for Christ.

There are some pro-life advocates, such as Dr. Bernard Nathanson,[1] who argue that full humanness begins when the conceptus is implanted in its mother's womb, which occurs within one week after conception. There are four basic arguments for this position to which I will respond.

  1. Not human life until it is recognized by another human?

    Nathanson argues that at the moment of implantation the unborn "establishes its presence to the rest of us by transmitting its own signals—by producing hormones—approximately one week after fertilization and as soon as it burrows into the alien uterine wall."

    For Nathanson implantation is significant because prior to this time the unborn "has the genetic structure but is incomplete, lacking the essential element that produces life: an interface with the human community and communication of the fact that it is there." [2]

    So, for Nathanson the unborn's hormonal communication to its mother is essential for humanness. I believe that this argument is flawed for at least two important reasons…

    First, how is it possible that one's essence is dependent on whether others are aware of one's existence? It seems intuitively correct to say that it is not essential to your being whether or not anyone knows you exist, for you are who you areregardless of whether others are aware of your existence. One interacts with a human being, one does not make a being human by interacting with it. In philosophical terms, Nathanson is confusing epistemology (the study of how we know things) with ontology (the study of being or existence).

    A second objection, which supports my first objection, is mentioned by Nathanson himself. He writes, "If implantation is biologically the decisive point for alpha's [the unborn's] existence, what do we do about the ‘test-tube’ conceptions? The zygote in these cases is seen in its culture dish and could be said to announce its existence even before it is implanted." Nathanson responds to these questions by asserting, "It seems to me that when it is in the dish the zygote is already implanted, philosophically and biochemically, and has established the nexus with the human community, before it is 're'-implanted into the mother's womb."[3]

    This response, however, does not support Nathanson's position, for he is admitting that there is no real essential difference between the implanted and the nonimplanted zygote, just an accidental difference (the former's existence is known while the latter's is not). Hence, just as there is no essential difference between a Donald Trump who is an unknown hermit and a Donald Trump who is an entrepreneur and billionaire (there are only accidental differences between the two Trumps), there is no essential difference between an unknown conceptus and a known conceptus.

    In sum, it seems counterintuitive to assert that one's essence is dependent on another's knowledge of one's existence.

  2. Do such things as hydatidiform moles, choriocarcinoma, blighted ovum, and clones prove that human life does NOT begin at conception?

    There is a second argument for implantation as the decisive moment: If we say that full humanness begins at conception, we must respond to the observation that “some entities that stem from the union of sperm and egg are not ‘human beings’ and never will develop into them,” and that there may be some human beings who come into being without the union of sperm and egg.[4]

    Nathanson gives examples of nonhuman entities that result from the sperm-egg union:

    • hydatidiform mole ("an entity which is usually just a degenerated placenta and typically has a random number of chromosomes")

    • choriocarcinoma ("a ‘conception-cancer’ resulting from the sperm-egg union is one of gynecology's most malignant tumors")

    • blighted ovum (“a conception with the forty-six chromosomes but which is only a placenta, lacks an embryonic plate, and is always aborted naturally after implantation”).

    A clone is an example of a human entity that may come into being without benefit of a sperm-egg union.[5]

    The problem with Nathanson's argument is that he confuses necessary and sufficient conditions. One who holds that full humanness begins at conception is not arguing that everything which results from the sperm-egg union is necessarily a conception. That is, every conception of a unique individual human entity is the result of a sperm-egg union, but not every sperm-egg union results in such a conception. Hence, the sperm-egg union is a necessary condition for conception, but not a sufficient condition.

    Furthermore, Nathanson is correct in asserting that it is possible that some day there may be human beings, such as clones, who come into existence without benefit of conception.


    But this would only mean that conception is not a necessary condition for full humanness, just as the sperm-egg union is not a sufficient condition for conception.

    In sum, Nathanson's argument from both nonhuman products of sperm-egg unions and the possibility of clones is inadequate in overturning the pro-life position that full humanness begins at conception.

  3. Spontaneous abortions

    It is estimated that twenty to fifty percent of all conceptions die before birth. Thirty percent, it is estimated, die before implantation.


    Some people argue that these facts make it difficult to believe that the unborn are fully human in at least the very earliest stage of their development prior to implantation. But this is clearly an invalid argument, for it does not logically follow from the number of unborn entities who die that these entities are not by nature fully human.

    Suppose the pro-choice advocate responds to this by arguing that if every fertilized ovum is human, then we are obligated to save all spontaneous abortions as well. But if we did, it would lead to overpopulation, death by medical neglect, and starvation. The problem with this response is that it confuses our obvious prima facie moral obligation not to commit homicide (that is, to perform an abortion) with the questionable moral obligation to interfere with natural death (that is, to permit the conceptus to abort spontaneously).

    Protecting life is a moral obligation, but resisting natural death is not necessarily a moral duty…There is no inconsistency between preserving natural life, opposing artificial abortion and allowing natural death by spontaneous abortion.[8]

    Admittedly, the question of interference in spontaneous abortions provokes the pro-life ethicist to think more deeply and sensitively about his or her position and to make distinctions and nuances that may not be pleasing to all who call themselves pro-life. But just as the difficult question of whether to pull the plug on the irreversibly comatose who are machine-dependent does not count against the position that murdering healthy adults is morally wrong, the question of how we should ethically respond to spontaneous abortions does not count against the pro-life ethic which says that we should not directly kill the healthy and normally developing unborn.

  4. Twinning and recombination.

    Some people argue that since both twinning (the division of a single conceptus) and recombination (the reuniting of two concepti) occur prior to implantation, individual human life does not begin until that time. However, a careful examination of the nature of twinning and recombination reveals that there is no reason to suppose that the original pre-twinned conceptus or any pre-recombined conceptus was not fully human.

    First, scientists are not agreed on many aspects of twinning.

    • Some claim that twinning may be a nonsexual form of parthenogenesis or “parenting.” This occurs in some animals and plants.

    • Others claim that when twinning occurs, an existing human being dies and gives life to two new and identical human beings like himself or herself.

      Photo copyrighted. Courtesy of Films for Christ.
    • Still others claim that since not all human concepti have the capacity to twin, one could argue that there exists in some concepti a basic duality prior to the split. Hence, it may be claimed that at least in some incipient form two individual lives were present from the start at conception.

    In any event, the fact of twinning does not seem to be a sufficient reason to give up the belief that full humanness begins at conception.[9]

    Second, every conceptus, whether before twinning or recombination, is still a genetically unique individual who is distinct from his or her parents.

    In other words, if identical twins result from a conceptus split or one individual results from two concepti that recombine, it does not logically follow that any of the concepti prior to twinning or recombining were not human.[10]

    To help us understand this point, philosopher Robert Wennberg provides the following story:

    Imagine that we lived in a world in which a certain small percentage of teenagers replicated themselves by some mysterious natural means, splitting in two upon reaching their sixteenth birthday. We would not in the least be inclined to conclude that no human being could therefore be considered a person prior to becoming sixteen years of age; nor would we conclude that life could be taken with greater impunity prior to replication than afterward. The real oddity—to press the parallel—would be two teenagers becoming one.

    However, in all of this we still would not judge the individual's claim to life to be undermined in any way. We might puzzle over questions of personal identity… but we would not allow these strange replications and fusions to influence our thinking about an individual's right to life. Nor therefore does it seem that such considerations are relevant in determining the point at which an individual might assume a right to life in utero." [11]


  1. Bernard Nathanson, M.D., Aborting America (New York: Doubleday, 1979), pp. 213-17. [up]
  2. Ibid., p. 216. [up]
  3. Ibid., p. 217. [up]
  4. Ibid., p. 214. [up]
  5. Ibid. [up]
  6. For a summary of the philosophical and scientific problems surrounding human cloning, see Andrew Varga, The Main Issues in Bioethics, Second edition (New York: Paulist Press, 1984), pp. 119-26. [up]
  7. As cited in John Jefferson Davis, Abortion and the Christian (Phillipsburg, NJ: Presbyterian and Reformed, 1984), p. 60. Cf. Thomas W. Hilgers, M.D., “Human Reproduction,” Theological Studies 38 (1977), pp. 136-52. [up]
  8. Norman L. Geisler, Christian Ethics: Options and Issues (Grand Rapids: Baker, 1989), p. 153. [up]
  9. Andrew Varga, The Main Issues in Bioethics, Second edition (New York: Paulist Press, 1984), pp. 64-65. [up]
  10. Ibid., p. 65. [up]
  11. Robert Wennberg, Life in the Balance: Exploring the Abortion Controversy (Grand Rapids: William B. Eerdmans Publishing Co., 1985), p. 71. [up]

Author: Francis J. Beckwith, adapted from a series in Christian Research Journal, Spring 1991. Provided with permission by Summit Ministries and the author.

Copyright © 1995, 1998, Christian Research Institute, 1991, 1998, All Rights Reserved—except as noted on attached “Usage and Copyright” page that grants ChristianAnswers.Net users generous rights for putting this page to work in their homes, personal witnessing, churches and schools.

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