Most modern schools of philosophy base morality on the principles of reason, and the principal accounts of moral development emphasize growth in moral reasoning rather than moral behavior. To be a human person in this sense would mean that an individual is conscious of his own existence and capable of making rational decisions, including the decision to remain alive.
On abortion and other forms of infanticide, Nature gives us the sort of answer she always gives–general rules and statistical averages to which there are exceptions, but, from the Christian perspective, Nature is the tarnished mirror in which we can only glimpse, obscurely, the true reality
The obligation to care for one’s offspring is a human universal, like the incest taboo or the prohibition of murder. Human and primate mothers, as a rule, devote themselves to their children, and mother-love is regarded conventionally as the most selfless and irrational forms of human attachment.