Many philosophic theories have developed to determine when human life begins. A large portion of these theories have been derived from a decisive moment position. The commonality between all decisive moment theories is simply what the name suggests. A particular moment or an established set of criteria determines when life begins. The only problem is that many "decisive moments" have been marked to signify the beginning of life. Following are short descriptions and supporting facts of some of the more common theories which have developed, along with the common arguments refuting these theories. The following information is paraphrased from Francis Beckwith (1994), and all quotations are his unless otherwise specified. The information taken from other people and sources can be found in the article written by Beckwith.
 

Dr. Bernard Nathanson believes                         Francis Beckwith offers two main
that life begins within one                            arguments in refutation of this
week after conception at the                           theory:
moment when the conceptus is
implanted in the mother's womb.
Two of his most convincing argu-
ments supporting this theory are:

  - At implantation, the unborn                         - One's essence is not de-
    "establishes its presence to                          pendent upon another person's
    the rest of us by transmitting                        awareness of you. "One inter-
    its own signals-by producing                          acts with a human being, but
    hormones-approximately one week                       one does not make a being
    after fertilization and as soon                       human."
    as it burrows into the alien
    uterine wall." This hormonal
    communication between the unborn
    and the mother is essential to
    humanness.

  - If human life is believed to begin                  - This argument confuses the
    at conception, then the entities                      sperm-egg union as a
    that are a result of the union between                necessary condition to con-
    egg and sperm, such as the hydatidi-                  ception, and not as a
    form mole (usually degenerated                        sufficient condition. If
    placenta with a random number of                      cloning of humans does become
    chromosomes), which never result in                   possible, it would only mean
    a human must be accounted for.                        that conception is no longer
    Humans who come into existence with-                  a necessary condition for
    out this union, such as a clone might                 full humanness.
    one day be, must also be  accounted for.
 
 

Professor Ernest Van Den Haag (1994)                 Francis Beckwith (1994) debates
makes an argument for the case that                  Professor Van Den Haag's position.
human life begins when the fetus in                  Beckwith argues that appearing
the womb begins to resemble a human.                 like a human is not a sufficient
According to Professor Van Den Haag,                 or a necessary condition for being
the acquisition of a functioning                     human. A mannequin resembles
brain and neural system soon after                   humans, but is not one. The
the first trimester cause the unborn                 bearded lady and the elephant man
being to begin to resemble an                        at the circus are more closely
embryonic being. These features are                  representative of nonhuman pri-
an essential part to being human, and                mates, yet they are human. "An
no group of cells should be seen as                  early embryo, though not looking
human until the functioning brain and                like a newborn, does look exactly
the neural system are present.                       like a human ought to look at this
                                                     stage in development.
 
 

- As a society, we begin to calculate                - In Chinese societies, one's age
  one's age at birth; thus, birth marks                is determined from the moment of
  the beginning of one's existence.                    conception. Does this mean that
                                                       American unborn babies are not
                                                       fully human while Chinese babies
                                                       are?

- After birth is when a child is                     - An abandoned child is not named,
  named, baptized, and an accepted                     baptized, or accepted into a
  member of a family.                                  family. Is he not human?
                                                     - The only difference between an
                                                       unborn entity and a newborn baby
                                                       is a difference in location.
                                                     - Robert Wennberg (1985) writes,
                                                       surely personhood and the right
                                                       to life is not a matter of
                                                       location. It should be what you
                                                       are, not where you are that
                                                       determines whether you have a
                                                       right to life.
 
 
 

Bioethicists such as Baruch Brody                   Beckwith has found one fundamental
often believe that life begins as                   difficulty with this line of
soon as the brain begins to                         reasoning:
function, which occurs approximately
40 to 43 days following conception.

- According to Brody, to determine                  - "Brain death indicates the end of
  if something can be classified as                   human life as we know it, the
  fully human, "we must first see . .                 dead brain having no capacity to
  . what properties are such that                     revive itself. But the develop-
  their loss would mean the going out                 ing embryo has the natural
  of existence (the death) of a human                 capacity to bring on the func-
  being." Brody concludes that                        tioning of the brain" (Andrew
  because brain death signifies the                   Varga 1984). The irreversible
  end of human existence, then the                    absence of brain waves
  beginning of human existence must                   signifies death; however, an
  occur when a functioning brain                      unborn entity has the capacity
  becomes present.                                    to have brain waves and cannot be
                                                      considered to be something other than
                                                      human based on this line of reasoning.
 
 
 

The time at which an unborn can                     Andrew Varga finds three main flaws
survive outside of the mother's                     in the viability theory:
womb is known as viability.
Viability is an often used deter-                   - First, "how does viability trans-
minant to mark the beginning of                       form the nature of the fetus so
life. Most people who support this                    that the nonhuman being then
theory will argue that "prior to                      turns into a human being?"
this time, since the unborn                           Viability is a measure of medical
cannot survive independent of her                     technology, the neonatal life-
mother, she is not a completely                       support system, and not a measure
independent human life and hence                      of humanity.
not fully human."                                   - Second, "is viability not just an
                                                      extrinsic criterion imposed upon
                                                      the fetus by some members of
                                                      society who simply declare
                                                      that the fetus will be
                                                      accepted at that moment as a
                                                      human being?"
                                                      Viability is an arbitrary
                                                      criterion that does not answer
                                                      the question of whether the fetus
                                                      is fully human.
                                                    - Third, "the time of viability
                                                      cannot be determined precisely,
                                                      and this fact would create great
                                                      practical problems for those who
                                                      hold this opinion."

Several ethicists today tend to                     Francis Beckwith also holds
set forth criteria which must be                    several objections to this theory
met before anyone can be consid-                    about when life begins.
ered fully human. Ethicists use
a couple different means to
defend this position:

- A distinction needs to be made                    - John Jefferson Davis writes, "Our
  between "being a human" and                         ability to have conscious
  "being a person." The homo sapiens                  experiences and recollections
  species does include the unborn;                    arises out of our personhood; the
  however, the unborn are not true                    basic metaphysical reality of
  persons because they have not yet                   personhood precedes the unfolding
  met a set of personhood criteria                    of the conscious abilities
  such as having feelings, awareness,                 inherent in it." Therefore, the
  and an interactive experience.                      unborn entity is a person simply
                                                      because it has the natural
                                                      capacity to function as a person.
                                                      Beckwith further supports this
                                                      idea: "The unborn are not
                                                      potential persons but persons
                                                      with much potential.

- Beckwith quotes ethicist Michael                  - Beckwith refutes this position
  Tooley to relate this theory to the                 by summarizing Jane English.
  issue of abortion. Tooley states                    "We consider it morally wrong
  that a being "cannot have a right to                to torture beings that are non-
  continued existence unless he                       persons, such as dogs or birds,
  possesses the concept of subject                    although we do not say these
  experiences, the concept of a tem-                  beings have the same rights as
  poral order, and the concept of                     persons." Thus even if the
  identity of things over time." Thus                 unborn is not viewed as a person,
  only those entities that function in                it still deserves the protection
  the desired way deserve the right to                that society is willing to bestow
  life.                                               upon completely nonhuman
                                                                                              entities.

       The above ultrasound portrays an 8 week old fetus. Many proponents of decisive theories do not believe that this fetus is a living human because it has not met all of the criterion that they have set forth.

    Many different theories exist which state that human life begins at a decisive moment. The number of decisive moments offered by various theories are numerous, though. According to these theories, life could begin as soon as the egg is implanted in the mother's womb, as soon as the unborn entity appears human, or once the unborn could survive outside the mother's womb. However, these theories are all based on reasoning; a lack of sound scientific evidence is apparent with each theory. Therefore, determining the beginning of human life in accordance with one of these theories becomes nearly impossible as people use logic to argue both sides of every issue.
 

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