While adherents of many religions profess that human life begins at the moment of conception, the doctrine of the Catholic Church is probably the clearest and most formal of all. Hence for Catholics and particularly for their most responsible spokesmen, the bishops, the crime of distancing themselves from the condemnatory sin of abortion is the greatest. And any fine distinction as to its being formed or unformed is not admissible among us. Though not formally proclaimed as a dogma of faith until 1854, the doctrine is found implicitly in the beliefs of many throughout the history of the Church. Why it took so long to make the belief definitive can perhaps be understood as the failure of many to accept the parallel between Mary and Eve, between Adam and Jesus.
Evil is opposed to good.
Mary was not in opposition to Jesus. For Catholics the existence of full human life from the moment of conception is not a matter of choice. The dogma of The Immaculate Conception is a binding doctrine of faith which concretely states that a new human person exists from the moment of each conception. When there is an obligation to act, the failure to perform the required act can be due either to simple non-choice or to deliberate choice. In all cases of voluntary omission , whether due to non-choice or deliberate choice, one is responsible for his failure to act, and the morality of the omission is determined in accord with the same norms that are applied to a positive choice to do something.