Chapter I Knowledge in general 1. Our knowledge knows only our ideas. Since the mind in all its thoughts and reflections has no immediate object other than its own ideas, which it is the only one to look at or contemplate, it is obvious that our knowledge knows only them. 2. Knowledge is the perception of agreement or disagreement of two ideas. Knowledge then seems to me to be nothing more than the perception of connection and agreement or disagreement and abomination of one of our ideas. That is the only thing it consists of. Where this perception is, there is knowledge, and where it is not, there, although we can imagine, guess or believe, but we still lack knowledge. Because if we know that white is not black, what else do we do but perceive that these two ideas do not coincide? If we have the greatest possible certainty of the proof that the three angles of a triangle are equal to two lines, what more do we perceive that equality with two lines necessarily coincides with and is inextricably linked to the three angles of a triangle? 3. This agreement or disagreement can be one of four types.
But to understand a little more clearly what this agreement or disagreement is, I think we can reduce everything to these four ways: I. Identity or diversity. II. Relationship. III. Coexistence or connection required. IV. Actual existence.
4. Identity or diversity of ideas. First, with regard to the first type of agreement or disagreement, namely identity or diversity. It is the first act of the mind, if it has feelings or ideas, to perceive its ideas; and to the extent that he perceives them, to know to each one what he is, and therefore also to perceive their difference, and that one is not the other. It is so absolutely necessary that without them there could be no knowledge, no argumentation, no imagination, no strong thought at all. As a result, the mind perceives each idea clearly and infallibly in order to agree with itself and be what it is; and all the different ideas to disagree, that is, to be one, not the other: and he does it without pain, work or deduction; but at first glance by its natural perceptual and distinctive power. And although the men of art have reduced this to these general rules, what is, is and it is impossible that the same thing is and is not, for voluntary application in all cases where there may be an opportunity to reflect on it: nevertheless, it is certain that the first exercise of this competence concerns certain ideas. A person knows infallibly, as soon as he always has them in his head, that the ideas he knows and calls are exactly the ideas they are; and that it is not other ideas that he calls red or square. Moreover, no maxim or statement in the world can allow him to know this more clearly or with more confidence than before, and without such a general rule. It is then the first agreement or disagreement that the mind perceives in its ideas; which she always perceives at first glance: and if there is any doubt about it, it will always be about the names and not about the ideas themselves, whose identity and diversity are always perceived, as quickly and clearly as the ideas themselves; and it cannot be otherwise. 5.
Abstract relationships between ideas. Second, the next type of agreement or disagreement that the mind perceives in one of its ideas can, in my opinion, be called relative and is nothing more than the perception of the relationship between two arbitrary ideas, regardless of their nature, whether they are substances, modes or others. For since all different ideas must be recognized forever as unequal and therefore universally and constantly denied to each other, there could be no place for positive knowledge if we could not perceive a relationship between our ideas and discover the agreement or disagreement they have with each other, in many ways the mind removes, compare them. 6. Their necessary coexistence in substances. Third, the third type of agreement or disagreement found in our ideas about which the perception of the mind is used is coexistence or non-coexistence in the same subject; and it is above all one of the substances. So when we say in relation to gold that it is fixed, our knowledge of this truth comes down to nothing more than that, this fixation or a force to remain unused in the fire is an idea that always comes with this particular type of yellowing, weight, foundryability, malleability and solubility in royal water that refers to our complex idea by the word gold. 7. . . .