When Does the Fetus Receive Its Soul…Thinking about the Talmud's answer ''When Does the Fetus Receive Its Soul''. The Article explains Judaism standpoint, but what about the Catholic standpoint?

According to the Kabbalah, a fetus receives its soul with the first three days after conception. This spiritual force illuminates it and engenders its growth. Without this, the ovum would simply decay. Terminating pregnancy even at an early stage is thus considered snuffing out the soul of a human being. See Rabbi Isaac Luria, Otzrot Chayim, Sha’ar A’nach , chap. 3.
source: http://goo.gl/KkzY3t

For us (Catholics) the answer is clear: life begins at conception. We need not try to determine "when" God infuses a soul. That is a metaphysical event, not a scientific one.

Аnd if the subject to grasp fully in all aspects of the Catholic point of view?

Ensoulment must occur at the moment of conception, for several reasons.

1. At the Incarnation, the Son of God assumed a human nature composed of a rational soul and a body.

Council of Ephesus: "For if it is necessary to believe that being God by nature he became flesh, that is man ensouled with a rational soul...."

Council of Ephesus: "We confess, then, our lord Jesus Christ, the only begotten Son of God, perfect God, and perfect man of a rational soul and a body, begotten before all ages from the Father in his godhead, the same in the last days, for us and for our salvation, born of Mary the virgin, according to his humanity, one and the same consubstantial with the Father in godhead and consubstantial with us in humanity, for a union of two natures took place."

The dogma is that, at the Incarnation, the Divine Nature was united to a full human nature, that is "man ensouled with a rational soul". 

Christ is like us in all things but sin, so His ensoulment of His human nature must have taken place just as ours does. 

2. The Saints and Doctors of the Church taught that at the Incarnation, the Divine Nature was united to the body and soul of Christ, and that the body (flesh) of Christ did not exist prior to that Incarnation. So there was no soulless body, awaiting ensoulment and awaiting Incarnation.

Saint Thomas Aquinas, citing Saint Gregory the Great: "On the contrary, Gregory says (Moral. xviii): 'As soon as the angel announced it, as soon as the Spirit came down, the Word was in the womb, within the womb the Word was made flesh.' "

Saint Thomas Aquinas, citing Saint John of Damascus: "On the contrary, Damascene says (De Fide Orth. iii): 'At the very instant that there was flesh, it was the flesh of the Word of God, it was flesh animated with a rational and intellectual soul.' "

Saint Thomas Aquinas: "On the contrary, Augustine says (De Fide ad Petrum xviii): 'Hold steadfastly, and doubt not for a moment that Christ's flesh was not conceived in the Virgin's womb, before being assumed by the Word.' " [Summa III Q 33 and 50]

3. In His human nature, Jesus is like us in all respects except for sin, and is consubstantial with us in humanity. Therefore, like the human nature of Christ, each human being is conceived such that body and soul are created in the same instant, and with body and soul united. The body is not created before the soul, nor is the soul created before the body; body and soul are created, as one human being, in the same instant. And the union of body and soul occurs at the same instant that both body and soul are created.

4. The Blessed Virgin Mary was preserved free from all effects of original sin at her conception. Original sin effects both body and soul. Therefore, in her conception three things occurred: the creation of her body (a single cell), the creation of her soul, and the preservation of both from the effects of original sin.

If ensoulment occurs after conception, then Mary would not have been preserved from the effects of original sin on the soul "in the first instant of her conception".

5. Specifically on the creation of the soul from conception:

Pope Pius XII: "The soul is not a person, but the soul, joined to the body, is a person." [Munificentissimus Deus, n. 32.]

Sacred Congregation for the Doctrine of the Faith: "Thus the fruit of human generation, from the first moment of its existence, that is to say from the moment the zygote has formed, demands the unconditional respect that is morally due to the human being in his bodily and spiritual totality. The human being is to be respected and treated as a person from the moment of conception; and therefore from that same moment his rights as a person must be recognized, among which in the first place is the inviolable right of every innocent human being to life."

Sacred Congregation for the Doctrine of the Faith: "The human being must be respected -- as a person -- from the very first instant of his existence." [Cardinal Ratzinger, CDF, Donum Vitae, I, 1.]

Therefore, every human being, beginning at the first instant of conception, is a human person, having both a body and a soul.