From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
These tendencies [to attempt to divorce concrete acts from a “fundamental option”] are therefore contrary to the teaching of Scripture itself, which sees the fundamental option as a genuine choice of freedom and links that choice profoundly to particular acts. By his fundamental choice, man is capable of giving his life direction and of progressing, with the help of grace, towards his end, following God’s call. But this capacity is actually exercised in the particular choices of specific actions, through which man deliberately conforms himself to God’s will, wisdom and law. It thus needs to be stated that the so-called fundamental option, to the extent that it is distinct from a generic intention and hence one not yet determined in such a way that freedom is obligated, is always brought into play through conscious and free decisions. Precisely for this reason, it is revoked when man engages his freedom in conscious decisions to the contrary, with regard to morally grave matter.
To separate the fundamental option from concrete kinds of behaviour means to contradict the substantial integrity or personal unity of the moral agent in his body and in his soul. A fundamental option understood without explicit consideration of the potentialities which it puts into effect and the determinations which express it does not do justice to the rational finality immanent in man’s acting and in each of his deliberate decisions. In point of fact, the morality of human acts is not deduced only from one’s intention, orientation or fundamental option, understood as an intention devoid of a clearly determined binding content or as an intention with no corresponding positive effort to fulfil the different obligations of the moral life. Judgments about morality cannot be made without taking into consideration whether or not the deliberate choice of a specific kind of behaviour is in conformity with the dignity and integral vocation of the human person. Every choice always implies a reference by the deliberate will to the goods and evils indicated by the natural law as goods to be pursued and evils to be avoided. In the case of the positive moral precepts, prudence always has the task of verifying that they apply in a specific situation, for example, in view of other duties which may be more important or urgent. But the negative moral precepts, those prohibiting certain concrete actions or kinds of behaviour as intrinsically evil, do not allow for any legitimate exception. They do not leave room, in any morally acceptable way, for the “creativity” of any contrary determination whatsoever. Once the moral species of an action prohibited by a universal rule is concretely recognized, the only morally good act is that of obeying the moral law and of refraining from the action which it forbids.
— Veritatis Splendor 67