PART THREE

APPLICATION OF THE CRITERION
TO DEMONSTRATE THE TRUTH
OF NON-PURE, OR MATERIATED KNOWLEDGE

CHAPTER 4

The certainty of the perception of bodies

1203. In the perception of ourselves, the two terms composing the judgment are given us entirely by nature. They are the predicate, being in all its universality, and the subject, myself, a real, substantial being. United in the unity of the perceiving subject, they form the intellective perception of myself. We cannot doubt this kind of intellective perception because the idea of being is an idea justified of itself - it is truth - and myself is the matter of our knowledge. This matter is not changed by our perception of it, because it is a feeling which is naturally just what it appears to be - because appearing is feeling. The simple perception of myself therefore admits only the application of the first principle of all knowledge, without any intermediate reasoning or use of a middle principle.

1204. The perception of bodies, however, is not so simple. When we feel bodies, we experience an action, an activity, carried out in us. But the agent is not presented to us as an ens simply in itself, independently of every relationship with any other ens. Feeling and all corporeal sensations make us feel this substance called body in its activity in us; we feel it in its special relationship with us, not simply in so far as it is, but in so far as it acts.

It is indeed true, therefore, that we perceive the action of a body solely as an experience; this is the way feeling presents the action to us. The understanding, however, sees this experience not from the point of view of one who experiences (this is the way sense experiences it) but from the point of view of one who acts, and therefore changes the experience into action for itself. It recognises contemporaneously an acting principle different from itself, and an ens or substance, whose only proper characteristic is action.

An ens is therefore supplied as something known solely by its action, not in itself. The mind supposes it because whatever acts must have the first act constituting it an ens; an act performed on another is a second act rooted in a first act. The fact that the second act entails the first is seen in being, because it is a truth belonging to the intrinsic order of being.
We must therefore find some justification for these intellective operations.

1205. I have shown elsewhere that 'experience' and 'action' express two relationships of the same thing. I have also shown that the understanding perceives an action in the experience undergone by feeling (cf. vol. 2, 666 ss.). This teaching gives rise to the following difficulty: 'Feeling perceives experience but not action. The understanding cannot perceive experience without action because, you say, the latter is included in the former. This seems to be a contradiction.'

I reply: 'It is true that feeling perceives experience but not action, because experience has a different existence from action. The understanding, however, perceives experience with the concept of experience. This concept cannot exist unless the concept of action is included in it. These are relative concepts: one is reciprocally included in the other'. In order to know what this concept of experience is, and how the understanding forms it, we will briefly recall the teaching given in volume 2.

1206. The principle of knowledge states: 'The object of the intellect is being', or equivalently: 'If the intellect understands, it must understand something' (vol. 2, 602 ss.).
When we, who are endowed with intellect, are conscious of a modification, we naturally say:(134) 'It is something which is not me.' We say this reasonably and necessarily: there must always be something, whatever it is, modifying us. We feel that a force is being applied, whether pleasantly or unpleasantly; and that which actually produces experience is not nothing. Therefore something or some entity is perceived.

At the same time we say: 'If something is present, a substance must be present, a first act which is the foundation of the ens', because every datum is in this sense either a substance or an appurtenance of substance - there is no middle term.(135) We see therefore that the perceived thing is in the experience undergone by feeling. It is an action in us, an agent, an acting agent in fact, because an agent can only be conceived as ens.

The difficulty therefore disappears. Sense can perceive the happening only as an experience, because the happening is not an objective potency. Sense can perceive an agent only by experiencing the agent; it cannot perceive it in any way with a relationship of action. But the understanding, which is the faculty of seeing things in themselves, necessarily sees the ens that is acting. This ens is, in so far as anything is in itself which acts: action is a consequence of being. Being is an essential activity, the first activity on which all other activities depend. It is therefore proper to the intellect always to see an action in an experience, an agent in the action, and an ens in itself (substance) in the agent (cf. vol. 2, 578 ss.); one thing is implied in the other, and is seen with a single act. This act is called an act of perception.

1207. We can now understand the concept of experience. It is an action considered relatively to the ens undergoing the action. The concept of experience embraces the concept of action; the former issues from the latter, just as the latter issues from the concept of agent. We can therefore conclude as follows. The perception of myself is made by means of two elements given by nature and brought together in an ens without the intervention of any faculty other than that of synthesis. Similarly, the perception of bodies is made by means of the union of two elements, given by nature, which unite through the faculty of synthesis aided by the faculty of integration. To the agent actually revealed in the experience integration adds the first act, which is conceived in every ens as its necessary foundation, constituting it an ens.
This first act however is determined solely by the action(136) produced by the act in our feeling.

1208. In the perception of bodies therefore we find: 1. the perception of myself with its modification or feelable experience; 2. the understanding perceiving the experience and acquiring the concept of experience; 3. the concept of experience comprising as its co-relative the concept of action; 4. the concept of actual action comprising an act and, therefore, an agent; 5. the agent mentally integrated through the need to conceive it as an ens.

The perception of myself with its modifications was justified in the previous chapter.
No demonstration is needed to show that the concepts of experience, action and agent are present in each other by implication, and that the understanding cannot have one without having simultaneously and at least implicitly the other two.
All we need to know is how the understanding passes from the concept of agent to the concept of ens. But we have already shown that being, naturally present to the human mind, is the universal means of knowing. We need only consider therefore that an agent is unknown if not conceived as an ens. This is the essential, universal function of the human mind. Thus, in the perception of bodies, the conception of the ens is logically anterior to that of agent, action and experience.

We said, however, that this fact involved some kind of integration, and in the following way. Because we need to conceive an agent, we have to unite being to the agent and thus apprehend it as an ens. But the mere concept of agent does not contain all that constitutes the ens; the first act is lacking because the ens first is, before acting in something different.

Thus, we add not only being in all its universality but the ens or basic first act of a body; this addition is an integration.
Note carefully that this first act, added to the agent through our need to conceive it, is nothing positive. The agent is always determined by its sensible action, which is the sole positive element we know in the perception of bodies. Hence, corporeal substance is specified by its sensible action alone, not by what we add to it through the need to conceive it. This sensible action is what takes the place of substance in bodies, and by its means they are what they are and receive their definition.

Because of this, we refrain from saying that the intellective perception of bodies involves an application of the principle of substance. What we understand as substance in them is not supplied; this is what is perceived by the senses. This perceived element is therefore the first specific act of bodies. The previous act, the pure form of ens, common to all entia, remains, but without specifying any ens.
At the same time it is clear that a body as perceived by a human being is an imperfect ens. It presents not the act by which it is an ens in itself, but the act by which it is an ens relative to feeling. This is why I call it extrasubjective ens.

(133) The sceptics directed their whole armoury against the perception of bodies, as I have already said. St. Augustine writes: Cum enim duo sint genera rerum quae sciuntur, unum earum quae per sensus corporis percipit animus, alterum earum quae per se ipsum (here we see how well St. Augustine distinguishes the two kinds of perception I have posited, which are the two sources of the matter of cognitions): multa illi philosophi garrierunt contra corporis sensus; animi autem quasdam firmissimas per se ipsum perceptiones rerum verarum, quale illud est quod dixi, Scio me vivere, nequaquam in dubium vocare potuerunt ['Two kinds of things are known, one of which is perceived by the spirit through the bodily senses, the other by the spirit through itself' (here we see how well St. Augustine distinguishes the two kinds of perception I have posited, which are the two sources of the matter of cognitions). 'Those philosophers have said many things against the bodily senses but have been unable to cast any doubt on the clear perceptions of true things which the spirit has through itself, such as the example I have given, "I know I am alive"'] (De Trinit., bk. 15, c. 12).

(134) As I have said, we are moved to do this by various needs and by our instincts (cf. vol. 2, 514 ss., 1030 ss.).

(135) I have amply shown the absolute necessity of this deduction in volume 2, 597 ss.

(136) 'Body' expresses an ens in so far as it carries out in us an action having a given mode (extension). If we considered the body ens, independently of its action, we would no longer be considering what we call 'body'. We must note this carefully, because it explains the term 'perception of bodies'. We say 'perception' in so far as 'body' expresses an agent acting on us. We must not turn body into an abstract, unknown or non-sensible being; if we do, its notion is destroyed. Hence, the physical effect is beyond all doubt, because it is understood in the very definition of body.