The conscience is always binding, but the conscience does not make right. Rather, it recognizes and applies it. A conscience must be formed that that it gives a true picture of objective right and wrong and its application to particular circumstances. Properly formed, conscience will lead one who has a right intention to choose the correct moral object in the given circumstances. “A morally good act requires the goodness of the object, of the end, and of the circumstances together” (CCC, 1755).
“The reason why a good intention is not itself sufficient, but a correct choice of action is also needed, is that the human act depends on its object, whether that object is capable or not of being ordered to God, to the One who ‘alone is good,’ and thus brings about the perfection of the person.” (VS, 78)
As noted by Saint Gregory of Nyssa: “All things subject to change and to becoming never remain constant… human life is always subject to change…it is the result of a free choice. Thus we are…, creating ourselves as we will, by our decisions” There is a hint of existentialism here, properly taught (as opposed to the atheistic existentialism of later thinkers like Jean-Paul Sartre and Ayn Rand). Action follows being, but likewise, what we do is what we are. The human, in acting, makes himself to be what he is: either he is one moving toward conformity to the image of God in which he was created, or he falls away from this end.
Given this, we must recognize that there are certain moral absolutes. Certain actions are always and everywhere right or wrong, because they are in conformity or denial of man as he should be.
“But this ordering to one’s ultimate end is not something subjective, dependent solely upon one’s intention. It presupposes that such acts are in themselves capable of being ordered to this end, insofar as they are in conformity with the authentic moral good of man.” (VS, 73)
We know that conscience is always binding, as stated above. However, it does not always excuse. When one acts in conformity with an erroneous conscience, he still sins objectively. Whether his ignorance is vincible or not will certainly determine the amount of culpability imputed to him, but it is every person’s responsibility to form the conscience, not just to follow it. Otherwise, we do what then Cardinal Ratzinger warned “relativism… seems the only attitude that can cope with modern times. We are building a dictatorship of relativism that does not recognize anything as definitive and whose ultimate goal consists solely of one’s own ego and desires.” (Homily of Cardinal Ratzinger, 18 April 2005). Without properly forming the conscience in authentic Catholic moral teaching, we move from an objective morality to a subjective one.
One such current moral theory that has been explicitly rejected in Veritatis Splendor is called proportionalism. Its proponents present it under the guise of objective and Catholic moral teaching, but it certainly is not so once carefully scrutinized. Proportionalism teaches that a physical evil can sometimes be knowingly committed while not being at the same time a moral evil. “Thus, in the concrete, one must always leave open the possibility that in some given set of circumstances, what would normally be a moral evil is not truly so, this is only a ‘physical’ or ‘ontic’ evil when it brings about greater goods or is justified by a proportionate reason for doing so.” (Moral Magisterium, Lesson 6)
A supporter of this theory might claim that, given the right circumstances, artificial birth control would not be a moral evil, but only a physical one. Perhaps the family has many children already, which it can barely feed. Would not the artificial prevention of another child, in this case, preserve the welfare of the family while still allowing the spousal exchange of love between the partners?
But the basic premise that “you may not do evil that good may come of it” is a basic Catholic moral teaching. In fact, the principle of natural law is “do good and avoid evil.” This cannot mean that some evil, done with a proportionally higher good end in mind (always subjective in its determination, by the way), is somehow permissible. Rather, a morally good act must have a morally good object as well as intention. Circumstances can change the intensity of the goodness or badness of the act, but do not determine it to be one or the other.
In our example of birth control, it is against natural law, because it artificially separates what God has made one: the act of spousal love and the possibility of procreation. Contrary to the question asked about “still allowing the spousal exchange of love between the partners,” it rather distorts this love. It becomes two people using each other as objects of pleasure. True love is self-sacrificial. The couple instead could, if for grave reasons, abstain to some degree such as would be the case with natural family planning, or even completely if necessary. This would show great love and conformity with God’s design for the marital act.
In brief, the moral object must always be good (or at least indifferent) as well as the intention. What we do, and not just the outcome we intend, is part of the moral act. “We must all appear before the judgment seat of Christ, so that each one may receive good or evil, according to what he has done in the body” (2 Cor 5:10, quoted in VS 73).
CCC = Catechism of the Catholic Church
VS = Veritatis Splendor (The Splendor of Truth)