What are Ideas?

We do not perceive objects outside of us by themselves. We see the sun, the stars, and an infinity of objects outside us; and it is not likely that the soul leaves the body and goes, so to speak, to wander in the heavens to contemplate all these objects. It therefore does not see them by themselves; and the immediate object of our mind, when it sees the sun, for example, is not the sun, but something that is intimately united to our soul, and this is what I call an idea. Thus, by this word idea, I mean here nothing else than what is the immediate, or closest, object of the mind when it perceives some object.

For the mind to perceive any object, it is absolutely necessary that the idea of that object be actually present to it.

But it is not necessary that there be outside something similar to this idea, for it very often happens that one perceives things that do not exist, and which have never even existed. Thus one often has in the mind real ideas of things that never were. When a man, for example, imagines a mountain of gold, it is absolutely necessary that the idea of this mountain be really present to his mind. When a madman, or a man with a burning fever, or one who is sleeping, sees some animal before his eyes, it is certain that the idea of this animal truly exists; but this mountain of gold and this animal never existed.

However, since men are naturally inclined to believe that only corporeal objects exist, they judge the reality and existence of things quite differently than they ought to; for when they feel an object, they want it to be very certain that this object exists, even though it often happens that there is nothing outside. They also want this object to be exactly as they see it, which never happens. But as for the idea, which necessarily exists and cannot be other than as it is seen, they ordinarily judge without reflection that it is nothing; as if ideas did not have a very great number of properties, as if the idea of a square, for example, were not very different from that of some number and did not represent entirely different things: which can never happen with nothingness, since nothingness has no properties. It is therefore undeniable that ideas have a very real existence. But let us examine what their nature and essence are, and see what can be in the soul capable of representing all things to it.

All things that the soul perceives are of two sorts: either they are in the soul, or they are outside the soul. Those that are in the soul are its own thoughts, that is to say, all its different modifications; for by these words, thought, manner of thinking, or modification of the soul, I generally mean all things that cannot be in the soul without it perceiving them through the inner sentiment it has of itself: such are its own sensations, its imaginations, its pure intellections, or simply its conceptions, its very passions and its natural inclinations. Now, our soul has no need of ideas to perceive all these things in the manner it perceives them, because they are inside the soul, or rather because they are only the soul itself in such and such a way; just as the real roundness of some body and its movement are only this body figured and transported in such and such a way.

But as for things that are outside the soul, we can only perceive them through the means of ideas, assuming that these things cannot be intimately united to it. There are two sorts of these: spiritual and material. As for spiritual things, there is some appearance that they can reveal themselves to our soul without ideas and by themselves: for even though experience teaches us that we cannot immediately and by ourselves communicate our thoughts to one another, but only through words or other sensible signs to which we have attached our ideas; one could say that God has ordained it thus only for the time of this life, in order to prevent the disorders that would presently occur if men could make themselves understood as they pleased. But when justice and order reign, and we are delivered from the captivity of our body, we may perhaps be able to make ourselves understood through the intimate union of ourselves, just as there is some appearance that angels can do in heaven. So that it does not seem absolutely necessary to admit ideas to represent spiritual things to the soul, because it may be that they are seen by themselves, although in a very imperfect way.

I do not examine here:

• how two spirits can unite with one another
• if they can in this way mutually discover their thoughts. I believe, however, that there is no purely intelligible substance except that of God; that nothing can be discovered with evidence except in His light; and that the union of spirits cannot render them mutually visible.

For, although we are very united with ourselves, we are and will be unintelligible to ourselves, until we see in God and He presents to us the perfectly intelligible idea He has of our being enclosed in His own. Thus, although it seems that I grant here that angels can by themselves manifest to one another both what they are and what they think, which at bottom I do not believe to be true, I warn that this is only because I do not wish to dispute about it, provided that one abandons to me what is incontestable, namely, that material things cannot be seen by themselves and without ideas [11].

I will:

• explain animal spirits in chapter 7
• show that at present we cannot know them entirely by themselves, although they may perhaps unite to us.

But I am speaking principally here of material things, which certainly cannot unite to our soul in the way that is necessary for it to perceive them; because being extended, and the soul not being extended, there is no relation between them.

Besides, our souls do not leave the body to measure the magnitude of the heavens, and consequently they can only see bodies from outside through ideas that represent them. This is something everyone must agree to.

Division of All the Ways by Which One Can See External Objects

I assert that it is absolutely necessary that the ideas we have of bodies and of all other objects that we do not perceive by themselves, either:

• come from these same bodies or objects
• or that our soul has the power to produce these ideas
• or that God produced them with it when creating it
• or that He produces them every time one thinks of some object
• or that the soul has in itself all the perfections it sees in these bodies
• or finally that it is united with a being all perfect, and which generally contains all intelligible perfections or all the ideas of created beings.

We can only see objects in one of these ways.