When Human Life Begins - The American College of Pediatricians
At the completion of the process of fertilization when the male and female pronuclei of the human progenitors sperm and ovum are indistinguishable and lose their nuclear envelopes, the human creature emerges as a whole, genetically distinct, individuated zygotic human organism. This individuated human organism actually has the natural capacity for the person-defining activities of reasoning, willing, desiring, and relating to others.So a blastocyst (a small group of cells inside an outer shell of cells) has the capacity for reasoning, willing, desiring and relating to others? There's no brain, heart or even placenta yet. They lost credibility right there.