When does a human person get their soul?

Question from MCM on 2/6/2008:  
When does a human person get their soul? What does the Catholic Church teach on this and where is it documented? I have been unable to locate a decisive answer in the Catechism. A friend is arguing with members of our family that the Catholic Church is unclear on when this occurs and that this vagueness possibly allows justifiable reason for artificial contraception and/or abortion early in pregnancy.
Answer by Judie Brown on 2/7/2008: 
Dear MCM

I love it when people divert attention from the scientific fact that a human being exists at the instant his life begins by arguing about that person receives his soul from God. However, there are valid theological explanations provided in several documents. For example, the Declaration on Procured Abortion which was issued by the Vatican in 1974, Footnote 19, states:

“The present Declaration deliberately leaves untouched the question of the moment when the spiritual soul is infused. The tradition is not unanimous in its answer and authors hold different views: some think animation occurs in the first moment of life, others that it occurs only after implantation. But science really cannot decide the question, since the very existence of an immortal soul is not a subject for scientific inquiry; the question is a philosophical one. For two reasons the moral position taken here on abortion does not depend on the answer to that question: 1) even if it is assumed that animation comes at a later point, the life of the fetus is nonetheless incipiently human (as the biological sciences make clear); it prepares the way for and requires the infusion of the soul, which will complete the nature received from the parents; 2) if the infusion of the soul at the very first moment is at least probable (and the contrary will in fact never be established with certainty), then to take the life of the fetus is at least to run the risk of killing a human being who is not merely awaiting but is already in possession of a human soul.”

Further, Pope John Paul II, in the Gospel of Life, paragraph 60, wrote:

"Furthermore, what is at stake is so important that, from the standpoint of moral obligation, the mere probability that a human person is involved would suffice to justify an absolutely clear prohibition of any intervention aimed at killing a human embryo. Precisely for this reason, over and above all scientific debates and those philosophical affirmations to which the Magisterium has not expressly committed itself, the Church has always taught and continues to teach that the result of human procreation, from the first moment of its existence, must be guaranteed that unconditional respect which is morally due to the human being in his or her totality and unity as body and spirit."

Finally the Catechism of the Catholic Church teaches:

365 The unity of soul and body is so profound that one has to consider the soul to be the "form" of the body: i.e., it is because of its spiritual soul that the body made of matter becomes a living, human body; spirit and matter, in man, are not two natures united, but rather their union forms a single nature.

I am sure these citations are sufficient and will at least challenge those who argue otherwise.

Judie Brown