Definitions

I. By the term “thought” (cogitatio, pensée), I comprehend all that is in us, so that we are immediately conscious of it. Thus, all the operations of the will, intellect, imagination, and senses, are thoughts. But I have used the word “immediately” expressly to exclude whatever follows or depends upon our thoughts: for example, voluntary motion has, in truth, thought for its source (principle), but yet it is not itself thought. [Thus walking is not a thought, but the perception or knowledge we have of our walking is.]

II. By the word “idea” I understand that form of any thought, by the immediate perception of which I am conscious of that same thought; so that I can express nothing in words, when I understand what I say, without making it certain, by this alone, that I possess the idea of the thing that is signified by these words. And thus I give the appellation idea not to the images alone that are depicted in the fantasy; on the contrary, I do not here apply this name to them, in so far as they are in the corporeal fantasy, that is to say, in so far as they are depicted in certain parts of the brain, but only in so far as they inform the mind itself, when turned towards that part of the brain.

III. By the objective reality of an idea I understand the entity or being of the thing represented by the idea, in so far as this entity is in the idea; and, in the same manner, it may be called either an objective perfection or objective artifice, etc. (artificium objectivum). For all that we conceive to be in the objects of the ideas is objectively [or by representation] in the ideas themselves.

IV. The same things are said to be formally in the objects of the ideas when they are in them such as we conceive them; and they are said to be in the objects eminently when they are not indeed such as we conceive them, but are so great that they can supply this defect by their excellence.

V. Everything in which there immediately resides, as in a subject, or by which there exists any object we perceive, that is, any property, or quality, or attribute of which we have in us a real idea, is called substance. For we have no other idea of substance, accurately taken, except that it is a thing in which exists formally or eminently this property or quality which we perceive, or which is objectively in some one of our ideas, since we are taught by the natural light that nothing can have no real attribute.

VI. The substance in which thought immediately resides is here called mind (mens, esprit). I here speak, however, of mens rather than of anima, for the latter is equivocal, being frequently applied to denote a corporeal object.

VII. The substance which is the immediate subject of local extension, and of the accidents that presuppose this extension, as figure, situation, local motion, etc., is called body. But whether the substance which is called mind be the same with that which is called body, or whether they are two diverse substances, is a question to be hereafter considered.

VIII. The substance which we understand to be supremely perfect, and in which we conceive nothing that involves any defect, or limitation of perfection, is called God.

IX. When we say that some attribute is contained in the nature or concept of a thing, this is the same as if we said that the attribute is true of the thing, or that it may be affirmed of the thing itself.

X. Two substances are said to be really distinct, when each of them may exist without the other.

Postulates

1st. I request that my readers consider how feeble are the reasons that have hitherto led them to repose faith in their senses, and how uncertain are all the judgments which they afterwards founded on them; and that they will revolve this consideration in their mind so long and so frequently, that, in fine, they may acquire the habit of no longer trusting so confidently in their senses; for I hold that this is necessary to render one capable of apprehending metaphysical truths.

2nd. That they consider their own mind, and all those of its attributes of which they shall find they cannot doubt, though they may have supposed that all they ever received by the senses was entirely false, and that they do not leave off considering it until they have acquired the habit of conceiving it distinctly, and of believing that it is more easy to know than any corporeal object.

3rd. That they diligently examine such propositions as are self-evident, which they will find within themselves, as the following:⁠—That the same thing cannot at once be and not be; that nothing cannot be the efficient cause of anything, and the like;⁠—and thus exercise that clearness of understanding that has been given them by nature, but which the perceptions of the senses are wont greatly to disturb and obscure⁠—exercise it, I say, pure and delivered from the objects of sense; for in this way the truth of the following axioms will appear very evident to them.

4th. That they examine the ideas of those natures which contain in them an assemblage of several attributes, such as the nature of the triangle, that of the square, or of some other figure; as also the nature of mind, the nature of body, and above all that of God, or of a being supremely perfect. And I request them to observe that it may with truth be affirmed that all these things are in objects, which we clearly conceive to be contained in them: for example, because that, in the nature of the rectilineal triangle, this property is found contained⁠—viz., that its three angles are equal to two right angles, and that in the nature of body or of an extended thing, divisibility is comprised (for we do not conceive any extended thing so small that we cannot divide it, at least in thought)⁠—it is true that the three angles of a rectilineal triangle are equal to two right angles, and that all body is divisible.

5th. That they dwell much and long on the contemplation of the supremely perfect Being, and, among other things, consider that in the ideas of all other natures, possible existence is indeed contained, but that in the idea of God is contained not only possible but absolutely necessary existence. For, from this alone, and without any reasoning, they will discover that God exists: and it will be no less evident in itself than that two is an equal and three an unequal number, with other truths of this sort. For there are certain truths that are thus manifest to some without proof, which are not comprehended by others without a process of reasoning.

6th. That carefully considering all the examples of clear and distinct perception, and all of obscure and confused, of which I spoke in my Meditations, they accustom themselves to distinguish things that are clearly known from those that are obscure, for this is better learnt by example than by rules; and I think that I have there opened up, or at least in some degree touched upon, all examples of this kind.

7th. That readers adverting to the circumstance that they never discovered any falsity in things which they clearly conceived, and that, on the contrary, they never found, unless by chance, any truth in things which they conceived but obscurely, consider it to be wholly irrational, if, on account only of certain prejudices of the senses, or hypotheses which contain what is unknown, they call in doubt what is clearly and distinctly conceived by the pure understanding; for they will thus readily admit the following axioms to be true and indubitable, though I confess that several of them might have been much better unfolded, and ought rather to have been proposed as theorems than as axioms, if I had desired to be more exact.

Axioms or Common Notions

I. Nothing exists of which it cannot be inquired what is the cause of its existing; for this can even be asked respecting God; not that there is need of any cause in order to his existence, but because the very immensity of his nature is the cause or reason why there is no need of any cause of his existence.

II. The present time is not dependent on that which immediately preceded it; tor this reason, there is not need of a less cause for conserving a thing than for at first producing it.

III. Anything or any perfection of a thing actually existent cannot have nothing, or a thing nonexistent, for the cause of its existence.

IV. All the reality of perfection which is in a thing is found formally or eminently in its first and total cause.

V. Whence it follows likewise, that the objective reality of our ideas requires a cause in which this same reality is contained, not simply objectively, but formally or eminently. And it is to be observed that this axiom must of necessity be admitted, as upon it alone depends the knowledge of all things, whether sensible or insensible. For whence do we know, for example, that the sky exists? Is it because we see it? But this vision does not affect the mind unless in so far as it is an idea, and an idea inhering in the mind itself, and not an image depicted on the fantasy; and, by reason of this idea, we cannot judge that the sky exists unless we suppose that every idea must have a cause of its objective reality which is really existent; and this cause we judge to be the sky itself, and so in the other instances.

VI. There are diverse degrees of reality, that is, of entity [or perfection]: for substance has more reality than accident or mode, and infinite substance than finite; it is for this reason also that there is more objective reality in the idea of substance than in that of accident, and in the idea of infinite than in the idea of finite substance.

VII. The will of a thinking being is carried voluntarily and freely, for that is of the essence of will, but nevertheless infallibly, to the good that is clearly known to it; and, therefore, if it discover any perfections which it does not possess, it will instantly confer them on itself if they are in its power [for it will perceive that to possess them is a greater good than to want them.]

VIII. That which can accomplish the greater or more difficult, can also accomplish the less or the more easy.

IX. It is a greater and more difficult thing to create or conserve a substance than to create or conserve its attributes or properties; but this creation of a thing is not greater or more difficult than its conservation, as has been already said.

X. In the idea or concept of a thing existence is contained, because we are unable to conceive anything unless under the form of a thing which exists; but with this difference that, in the concept of a limited thing, possible or contingent existence is alone contained, and in the concept of a being sovereignly perfect, perfect and necessary existence is comprised.

Proposition I

The existence of God is known from the consideration of his nature alone.

Demonstration

To say that an attribute is contained in the nature or in the concept of a thing is the same as to say that this attribute is true of this thing, and that it may be affirmed to be in it. (Definition IX)

But necessary existence is contained in the nature or in the concept of God (by Axiom X).

Hence it may with truth be said that necessary existence is in God, or that God exists.

And this syllogism is the same as that of which I made use in my reply to the sixth article of these objections; and its conclusion may be known without proof by those who are free from all prejudice, as has been said in Postulate V. But because it is not so easy to reach so great perspicacity of mind, we shall essay to establish the same thing by other modes.

Proposition II

The existence of God is demonstrated, a posteriori, from this alone, that his idea is in us.

Demonstration

The objective reality of each of our ideas requires a cause in which this same reality is contained, not simply objectively, but formally or eminently (by Axiom V).

But we have in us the idea of God (by Definitions II and VIII), and of this idea the objective reality is not contained in us, either forrnally or eminently (by Axiom VI), nor can it be contained in any other except in God himself (by Definition VIII).

Therefore this idea of God which is in us demands God for its cause, and consequently God exists (by Axiom III).

Proposition III

The existence of God is also demonstrated from this, that we ourselves, who possess the idea of him, exist.

Demonstration

If I possessed the power of conserving myself, I should likewise have the power of conferring, a fortiori, on myself, all the perfections that are awanting to me (by Axioms VIII and IX), for these perfections are only attributes of substance, whereas I myself am a substance.

But I have not the power of conferring on myself these perfections, for otherwise I should already possess them (by Axiom VII).

Hence, I have not the power of self-conservation.

Further, I cannot exist without being conserved, so long as I exist, either by myself, supposing I possess the power, or by another who has this power (by Axioms I and II).

But I exist, and yet I have not the power of self-conservation, as I have recently proved. Hence I am conserved by another.

Further, that by which I am conserved has in itself formally or eminently all that is in me (by Axiom IV).

But I have in me the perception of many perfections that are awanting to me, and that also of the idea of God (by Definitions II and VIII). Hence the perception of these same perfections is in him by whom I am conserved.

Finally, that same being by whom I am conserved cannot have the perception of any perfections that are awanting to him, that is to say, which he has not in himself formally or eminently (by Axiom VII); for having the power of conserving me, as has been recently said, he should have, a fortiori, the power of conferring these perfections on himself, if they were awanting to him (by Axioms VIII and IX).

But he has the perception of all the perfections which I discover to be wanting to me, and which I conceive can be in God alone, as I recently proved:

Hence he has all these in himself, formally or eminently, and thus he is God.

Corollary

God has created the sky and the earth and all that is therein contained; and besides this he can make all the things which we clearly conceive in the manner in which we conceive them.

Demonstration

All these things clearly follow from the preceding proposition. For in it we have proved the existence of God, from its being necessary that some one should exist in whom are contained formally or eminently all the perfections of which there is in us any idea.

But we have in us the idea of a power so great, that by the being alone in whom it resides, the sky and the earth, etc., must have been created, and also that by the same being all the other things which we conceive as possible can be produced.

Hence, in proving the existence of God, we have also proved with it all these things.

Proposition IV

The mind and body are really distinct.

Demonstration

All that we clearly conceive can be made by God in the manner in which we conceive it (by foregoing Corollary). But we clearly conceive mind, that is, a substance which thinks, without body, that is to say, without an extended substance (by Postulate II); and, on the other hand, we as clearly conceive body without mind (as every one admits):

Hence, at least, by the omnipotence of God, the mind can exist without the body, and the body without the mind.

Now, substances which can exist independently of each other, are really distinct (by Definition X).

But the mind and the body are substances (by Definitions V, VI, and VII), which can exist independently of each other, as I have recently proved:

Hence the mind and the body are really distinct.

And it must be observed that I have here made use of the omnipotence of God in order to found my proof on it, not that there is need of any extraordinary power in order to separate the mind from the body but for this reason, that, as I have treated of God only in the foregoing propositions, I could not draw my proof from any other source than from him: and it matters very little by what power two things are separated in order to discover that they are really distinct.