SECTION SEVEN

THE FORCES PRESENT IN A PRIORI REASONING

CHAPTER 5

A priori reasoning leads us to logical principles
that appertain to the order of ideal beings

1446. I call a priori knowledge that which descends from the idea of being, the form and supreme rule of reason.

1447. I call pure a priori knowledge that which not only descends from the idea of being, but also descends from it without need of any datum of internal or external experience. It is, therefore, knowledge which can be found on analysis in being itself, or can be deduced from it in the way that a condition can be deduced from that on which it is conditional.

1448. The analysis of pure being is conducted without the intervention of any datum of experience. It does not allow us, therefore, to distinguish within this being anything except the characteristics of unity and perfect simplicity. In this way we find as given in the primal idea 1. its first activity, which is that of being; and 2. the essential characteristic of this first activity, which is that of absolute unity.(321) All our pure a priori knowledge is reduced to these two notions, and to a few others which we have indicated elsewhere. Such knowledge shows us how unity stands at the spring of intellective knowledge, enabling us to understand how all true unity comes from the intellect, and how human cognitions share in that marvellous unity.

1449. Multiplicity is an a posteriori cognition, that is, one given by experience. Not only is it not contained in ideal being, but it cannot even be deduced from it by reasoning alone. Although the acts with which the spirit reflects on being can be repeated, they all end in the same, identical being, which cannot be seen to be multiplied unless it is considered in relationship with the various acts of the spirit constituting the beginning of experience.
In addition to analysis, pure a priori reasoning can also be employed on being. But we will speak about this in the next chapter.

1450. Being that we see comes to completion and terminates in various limited ways when it is applied to the data provided by experience. Human knowledge is constituted in this way.
We know three kinds of things: 1. entia which subsist in themselves, without reference to the mind, such as bodies; 2. feelings; 3. ideal entia, essences. The first two constitute the matter of our knowledge; the third, the form. Everything formal in knowledge is a priori knowledge (cf. vol. 1, 304-309, 325-327). Let us now examine the extent of this knowledge.

1451. Being takes other names as soon as it is considered in its different relationships. These names express the relationships in which it is beheld. If being is seen as the fount of intellective knowledge, it is called truth; if it is considered as the first activity, capable of being completed with subsistence and essentially lovable, it is called good or perfection.
The ideas of what is true and of what is good arise, therefore, from the very first application of being, and constitute the two most general aspects in which the idea of being is presented in its applications. These ideas correspond to the two modes of essences, that is, in the mind and outside the mind. Being in its application in the mind as the fount of knowledge is truth; being in its application outside the mind as the fount of lovable subsistence is good.

1452. Truth, therefore, is the general relationship of being with other cognitions, all of which call being into play as their support and criterion. Let us consider the partial modes taken by being in its partial applications.
First, we have seen that pure a priori knowledge, given by the analysis of being, contained two elementary ideas, the basis of all knowledge: 1. the idea of the activity which is ideal being; and 2. the idea of absolute unity. Consequently there are two series of principles in the application of being, according to the two elements which compose it.(322)

Considered positively as activity, being takes the form of the four principles of cognition, contradiction, substance and cause that we have already expounded (cf. vol. 2, 559-569).

Considered as absolute unity, being is the first element and foundation of the idea of quantity, and is then transformed into the principles that govern quantity such as 'the whole is greater than its parts', and other principles of this kind, on which mathematical sciences rest.

1453. Briefly, in its application, being is changed and ends in all the essences of things. These essences are the principles of all the branches of knowledge, as antiquity had already affirmed.(323) The idea of being, therefore, is the fount and firm foundation of all human learning.
However, all these principles are in the order of ideas. Can we pass, therefore, from the idea of being to the sphere of reality? Does this idea possess any interior force enabling us to push beyond it? These are the questions which we must examine in the following chapters. But first we shall confirm, with a new proof, the truth that what is deduced from being is deduced a priori because being itself is not produced by any abstraction, but given by nature.

(321) Absolute unity does not exist separate from the idea of being. We would not have imposed on it another word, unity, different from that which we give to being, if the exclusion of multiplicity from being had not been necessary. In so far as unity is considered separately from being, it indicates only a negation, the negation of multiplicity. This explains the futility of so much speculation on unity, which lacks foundation because it considers unity as something in itself, divided from being.

(322) This is not true composition. Unity is nothing of itself except the deletion of multiplicity, and does not therefore offend the simplicity of being. On the contrary, it is the very simplicity of being. But language of its nature leads to equivocal expressions. It indicates with a word not only that which is, but also the negation of that which is. Indicated in this way, even nothing appears to be something.

(323) 'The principle of all knowledge that human reason can have of anything,' says St. Thomas, 'is the concept of the thing's substance' (the essence), 'because the principle of demonstration is simply the essence itself of the thing.' (C. G., I, q. 3).