Chapter 5

HOW WE SEE TRUTH

1055. We have seen that there are two principles of certainty, one intrinsic, the other extrinsic. The intrinsic principle is the intuitive knowledge of truth; the extrinsic, the knowledge of a sure sign of truth.
The extrinsic principle is never the ultimate principle; it is ordered to, and dependent on the intrinsic principle because a sure sign of truth cannot exist without a preceding certainty. And this certainty can only be given in the last analysis by the intuitive knowledge of truth (cf. 1054). Hence, the supreme or ultimate principle of certainty is one only, the intuition or vision of truth.

1056. We must now explain how it is possible for us to see, that is, to know intuitively, the truth of a proposition.
We say we know the truth of a proposition when we know the reason for it. But the reason for a proposition can be expressed by another proposition; for example, the reason for the proposition `The human being is the noblest of animals' can be expressed by the proposition `Because the intelligence with which the human being is endowed is more noble than feeling'.

But if one proposition provides the reason for another, a third may provide the reason for the second: the reason for the reason, the explanation of the explanation. Thus, the reason for the proposition `Intelligence is a more noble faculty than feeling' is given by the proposition `Because intelligence has being in general as its object, while feeling is confined to a body'. If, in order to say we know the truth of the third proposition, we need to know its reason, we will need a fourth proposition to express it.

The same argument, however, will require us to look for the reason for the fourth proposition, and then the reason for the fifth, and so on. Eventually we will come to a final proposition beyond which we cannot go because it contains and expresses the supreme reason. This supreme reason must satisfy us of itself (when it is well understood), and completely assuage our desire for reasons. It is the real reason for the whole series of propositions and therefore the reason even for the first proposition whose truth we cannot say we know intuitively until we have reached it in its ultimate reason where the intellect is fully satisfied.

1057. Our closest attention is necessary here. We wish to know `when it is that we intuitively apprehend the truth of a proposition'. Observation of fact reveals that the human understanding is not completely satisfied and at rest, nor does it believe and say it sees the truth of a proposition, until it has seen the ultimate reason for the proposition. The truth therefore of any proposition which is not the ultimate proposition, is not the proposition itself but its ultimate, supreme reason. And this ultimate reason is called (according to the common meaning of the word) `truth' of the proposition. To see the truth is simply to see this reason.

1058. The criterion of certainty, therefore, expressed in the words `the intuitive knowledge of truth' can equally be expressed as `knowledge of the ultimate reason for the proposition' (14) under consideration.

Notes:

(14) I say `of the proposition' and not `of the subject matter of the proposition'. The reason for the proposition is a logical reason; the reason for the subject matter of the proposition is a metaphysical reason or final reason, etc. For example, in the proposition `The human race exists', the human race is the subject matter. To be certain about this proposition, I have no need at all to know the ultimate reason for the human race but simply the ultimate reason that proves its existence. The proposition concerns the existence, not the origin or reason of the human race.