The three moral determinates of the human act are the object, the end (or intention), and the circumstances. For an action to be morally good, all three determinates must be good. A lack in any of them will, at least in a qualified way, make the morality of the act to be bad.
The object of the human act is that which is actually done. From this, we get the character of the objective morality. There are actions that are objectively in conformity or not in conformity with the created human person, and thus, actions in conformity with them or against them are objectively good or evil as such.
For example, the object of murder is the taking of an innocent life. Murder is objectively wrong, and thus the taking of an innocent life is never morally good. No intention or circumstances can make it to be otherwise, and this is because of its basis in reality itself. It is the eternal law, which we are created under, that establishes this objective moral order, and we and our actions are, by our very creation, subject to this eternal law.
However, the subjective nature of us as human may reduce the culpability of our action if we do not know that the object of our action is morally evil. While this cannot change the objective nature of the act, one may be more or less morally responsible for the good or evil of the action based on one’s knowledge of the objective character of the act.
The second moral determinate is the intention, and this is the purpose or motive for which the agent acts. While a wrong intention can make a morally good act subjectively wrong and cause culpability in the agent, a good intention can never make an objectively evil act to be good. The end does not justify the means.
All intentions should be in conformity to the objective truth, and again this is to be found in the eternal law. Humans first of all find this “written in their hearts” and this participation of the rational creature in the eternal law is called the natural law. Conscience is closely related to this, as it is a judgment of reason. Our intentions, then, must be in conformity with our conscience. Besides the natural law, we also have the revealed truths from God, and we are obligated to form our conscience in accordance with both. Our culpability in this is only known perfectly by God.
The circumstances of an action are individual conditions of specific acts in time and place that are not of themselves part of the nature of the action. They do, however, modify the moral quality of the action. The who, what, when, and where of actions are bearing on the goodness or otherwise of specific actions. These circumstances cannot, of course, make an objectively evil action to be good, but they can increase or decrease both moral culpability and the degree of goodness or evil in the act.
Prudence is important here, and this virtue helps us to take correct actions in particular circumstances. Conscience as well includes an act of judgment, and thus it applies not only to the morality of the object and intentions of the act, but is closely tied with the particulars of the acts in a given situation or circumstance.
Briefly, it may be said that law, which all law has its foundation in the eternal law, is the norm by which all objective truth is measured. Likewise, conscience is closely related to our participation in the eternal law, first by way of the natural law and also by our understanding of revealed truth. Conscience then, while its purpose is to lead man to perform actions in accordance with objective truth, can be said to be on the side of his subjective culpability.
God knows the hearts of men, and men may be said to be judged by their intentions. This, however, has a qualifier. Among the intentions of men must be included the intention to form their consciences with objective truth. We will thus be culpable for seeking the truth, and a willful neglect of seeking the objective morals is itself an evil, for man, being rational, must seek the truth. A being must act in accordance with its nature, and this means that a rational being must act with reason.
We are always obliged to follow our conscience, but we are also responsible to form it according to the law. “Conscience has rights because it has obligations.”