The sacredness of human life is at the center of Catholic dogma, but often creates some confusion when discussing the issues of stem cell research or human cloning; both being medical technologies that are presented as being of help to humanity.
In this piece from the EWTN library, first published in L’Osservatore Romano, the theologian from the Papal Household reflects on cloning and helps us understand why it is forbidden within Catholicism.
An excerpt.
“The transmission of human life has always been viewed as a mystery, not in the sense that the biological functions were unknown, but in the sense that there is something great and inscrutable happening in this moment that cannot be fully fathomed by empirical observation and deserves respect. Human life is marked by an inherent sanctity. For this reason the transmission of human life is distinguished semantically from the transmission of the life of plants and animals. One is called "procreation" and the other is called "reproduction". The prefix pro- in procreation refers to a vicarious function. It is God who creates out of nothing an immortal human soul and gives it to every child that is conceived. This divine gift is received not only by the child that begins its human existence. It is also received in the moral sense by the parents of the child who fulfil the gravest mission of transmitting life (cf. the opening lines of Paul VI's Encyclical: Humanae vitae tradendae munus gravissivum) and of loving and educating the child that they have received from God. And even if the parents fail in their responsibilities, God does not fail because "God never takes back his gifts or revokes his choice" (Rom 11:29). When the conceiving of a child takes place as a result of sinful adultery, incest, rape or is in vitro, God continues to create an immortal soul for the child, even though the participation of the parents in this transmission of human life is tainted by egoism, aggression, irresponsibility or manipulative pride. The transmission of the life of plants and animals is different, because plants and animals have no immortal soul and so no personal dignity, and that is why it is simply termed "reproduction". They exist not only for themselves but ultimately in view of the needs of humanity (cf. Gn 1:28-29).”