How does one come to know the general determinations of the first principle of practical reasoning? This question can be considered on two levels. On one level, the question is how anyone directly and practically knows that human life, for example, is good and death is bad. On another level, the question is a methodological one: How is a definite list arrived at? How could it be checked? This second, methodological question was treated above (5‑D).
As to the first question, practical insight into the various forms of human fulfillment cannot be derived from any more general knowledge. One does not come to know these goods by deducing them from prior principles. But neither is knowing them a matter of experience in the sense that knowing fire burns is a matter of experience. To know that fire burns is to understand something which is the case. To know that life is a good is to understand something of human possibility. In practice life is understood as good only insofar as it is to be realized or is threatened and needs to be protected. How can one understand on the basis of experience what is not actual but only potential?
This question can be answered only if one realizes that human intelligence does not become practical merely by its subject matter, nor merely by being moved by will or inclination. Reason is practical by nature just as much as it is theoretical by nature. And just as theoretical thought by its very nature is thinking that-it-is, so practical thinking by its very nature is thinking that-it-would-be-well-to-be. Facing the world, one not only wonders, “What is so and not so?” but also, “What might I bring about or not bring about?” Underlying the theoretical question is a frame of mind which can be expressed: What is so must be affirmed, and what is not so must be denied. Underlying the practical question is a frame of mind which can be expressed: Good is to be done and pursued, and evil is to be avoided.36
With this practical presupposition in mind, people experience their tendencies and understand in them possibilities which could be satisfied by action. The tendencies, simply as psychic facts, are not themselves knowledge of human goods. Tendencies might move one to action, but they are no more reasons for acting than are any other facts. However, in the experience of tendencies, human understanding which is oriented toward possible action grasps the possible fulfillments to which the tendencies point. Thus one forms, naturally and without reflection, the truth: Such-and-such is a good.
A practical truth grasped in this way is so basic and so obvious that it is seldom stated expressly or considered by itself. People who become aware that food is becoming scarce think they must try to ensure their supply. Underlying this thought is awareness of a fact—food is necessary for survival—and the practical truth: Life is to be preserved.
Some tendencies can be at least partly satisfied by nature and by the action of other persons. The process of gaining insight into goods partly depends upon this fact. In experiencing a tendency and its satisfaction, one learns factual truths which provide a background for the practical insight. Thus, for instance, children are naturally curious and naturally grow in understanding as they ask and answer questions. Insight into this process provides a basis for the practical insight that knowledge is a good which can be pursued by one’s own deliberate action. However, this insight cannot be derived from nonpractical awareness. Practical awareness is an irreducible starting point of self-actualization, which is a creative process of exploring and realizing one’s own possibilities by one’s own initiative.
To the extent that the understanding of basic forms of human goodness is a projection of possibilities implicit in one’s naturally given tendencies, this understanding is stable and invariant. Thus the concept of truth as a good remains an invariant framework insofar as this practical insight corresponds to natural curiosity, for such curiosity does not change.
However, any experience of fulfillment in any basic form of goodness leads to some specification of interest. The child at first asks questions about everything, but later wonders only about certain subjects. Moreover, experience of fulfillment together with theoretical inquiry leads to more or less detailed practical sketches of the basic goods. Truth, for example, is articulated into a set of fields of study. The secondary parts of the understanding of the basic forms of human goodness can develop and vary, and they can include mistakes and thus be open to correction.
What is true of goods such as life and truth also is true, mutatis mutandis, of the personal and interpersonal goods of the existential domain. The various levels of existential harmony are understood as good on the basis of human tendencies no less fundamental than the urges to survive, to play, and to understand. For everyone wants peace of mind, friends, and a favorable relationship with unseen Power. But differences in experience and in theoretical beliefs make a great difference in how people conceive these goods in specific detail.