RAREFACTION
Whenever we see that a body is rarefied, we ought to think that there are many intervals between its particles, which are filled with some other body.
Principles, II, 6. IX2, 66.
We ought not to have more difficulty in believing that rarefaction takes place as I have said, even though we do not perceive the body which fills [the pores of the rarefied body] by any of our senses, because there is no reason which obliges us to believe that we have to perceive all the bodies which are around us by means of our senses, and because we see that it is very easy to explain it in this way, and because it is impossible to conceive it otherwise.
Principles, II, 7. IX2, 67.
RATS
Rats are engendered or made by accident in garbage.
Letter to Regius, Dec., 1641. III, 460.
REAL DISTINCTION
There can be said to be a real distinction between two substances when each of them can exist without the other.
Replies, II. IX, 125.
REALITY
There are various degrees of reality or entity: for substance has more reality than accident or mode, and infinite substance than finite. This is why there is also more objective reality in the idea of substance than in that of accident, and in the idea of infinite substance than in the idea of finite substance.
Replies, II. IX, 128.
REASON
Anyone who seriously wishes to search out the truth of things should not choose any particular science; for they are all united among themselves by a reciprocal interdependence; rather, he ought to think only of developing the natural light of his reason, not in order to resolve some difficulty or other of the School, but so that his understanding may show to his will the choice that it must make on every occasion of his life.
Rules, I. X, 361.
Nothing seems more absurd to me than to dispute rashly about the secrets of nature, about the influence of the stars upon our inferior regions, about the prediction of the future, and other things of that kind, as so many people do, without ever having asked whether human reason is capable of resolving these questions.
Rules, VIII. X, 398.
The power of right judgment, and of distinguishing the true from the false, which is properly what is called good sense or reason, is naturally equal in every man.
Discourse, I. VI, 2.
I would believe that reason, insofar as it is the only thing which makes us men, and distinguishes us from the beasts, is entirely complete in everyone.
Discourse, I. VI, 2.
Reason is a universal instrument, which can be used in all kinds of situations.
Discourse, V. VI, 57.
Not only do beasts have less reason than men; they do not have it at all.
Discourse, V. VI, 58.
If we always do everything that our reason dictates to us, we will never have any cause for repenting, even though the outcome makes us see, afterward, that we were deceived, because [the error] is not our fault.
Letter to Elisabeth, Aug. 4, 1645. IV, 266.
It is not necessary that our reason never deceive us; it is enough that our conscience testify that we have never lacked resolution and virtue, to execute all the things that we have judged best, and thus virtue alone is sufficient to make us content in this life.
Letter to Elisabeth, Aug 4, 1645. IV, 266-267.
The true use of our reason for the conduct of our life consists only in examining and considering without passion the value of all the perfections, those of body as well as those of the mind, which can be acquired by our conduct, such that, since we are ordinarily obliged to deprive ourselves of some of them, in order to have the others, we always choose the best.
Letter to Elisabeth, Sept. 1, 1645. IV, 286-287.
As we were born men before we became Christians, it is beyond belief that any man should seriously embrace opinions which he thinks contrary to the right reason that constitutes a man, in order that he may cling to the faith through which he is a Christian.
Notes against a Program, IV. VIII 2, 353-354.
What knowledge we have or acquire by the route that our reason takes has, first, the murkiness of the principles from which it is derived, and, in addition, the uncertainty which we find in all our reasonings.
Letter to Newcastle, Mar. or Apr., 1648. V, 137.
See intuition; natural light.
REASON, BEINGS OF
It is not true [that God is a being of reason] if by being of reason one understands something which does not exist, but only if all the operations of the understanding are taken as beings of reason, that is, as beings which share in reason.
Replies, II. IX, 106.
REASON, DISTINCTIONS OF
The distinctions of reason [or distinctions made by thought] consist in the fact that we sometimes distinguish a substance from some one of its attributes, even though it is not possible for us to have a distinct knowledge of it; or rather in the fact that we try to separate two such attributes from the same substance while thinking of one without thinking of the other.
Principles, I, 62. IX2, 53.
REASON, FORMAL
I proved nothing else by the example of the wax [in the second Meditation] than that the color, the hardness, the shape, etc., did not belong to the formal reason of the wax, i.e., that one could conceive everything that could be found to be necessarily in the wax, without having need of thinking of these.
Replies, III. IX, 136.
REASON, NATURAL
Those who use only their pure natural reason will better judge my opinions than those who believe only in ancient books.
Discourse, VI. VI, 77.
REASONING
Because there are some men who despise reasoning, even in connection with the simplest matters in geometry, and make errors there, judging that I was subject to failure as much as anyone else, I rejected as false all the reasonings that I had previously taken for demonstrations.
Discourse, IV. VI, 32.
REFRACTION
In order to determine their quantity [i.e. measure refraction], insofar as it depends upon the particular nature of the bodies in which it takes place, it is necessary to go to experience.
Dioptrics, II. VI, 102.
REFUTE
There are only two ways to refute what I have written: one is to prove by some experiments or reasons that the things which I have supposed are false; and the other that what I have deduced from these suppositions should not have been deduced.
Letter to Mersenne, May 17, 1638. II, 143.
REGRET
Regret is a species of sadness, which has a particular bitterness, in that it is always joined to some despair, and to the memory of the pleasure that enjoyment has given us.
Passions, III, 209. XI, 484-485.
RELATIVE
As for the relative, it is that which participates in the same nature, or at least in some one of its aspects; because of this it may be connected to the absolute, and be deduced from it through a chain of reasonings; but, in addition, it contains in its concept other things which I call relations: of this nature is everything which is called dependent, effect, composite, particular, multiple, unequal, dissimilar, oblique, etc.
Rules, VI. X, 382.
See absolute.
REMORSE
If one determines to do some action before irresolution has been overcome, that gives birth to remorse of conscience: it does not have to do with the time to come, as do the preceding passions, but with the present or the past.
Passions, II, 60. XI, 376.
Remorse of conscience is a species of sadness, which comes from the suspicion that something that one is doing, or has done, is not good.
Passions, III, 177. XI, 464.
REPENTANCE
It seems to me that there is no reason for repentance if one has done what he judged to be the best at the time when he had to resolve upon its execution, even though, afterward, rethinking it with greater leisure, he judges it to have been an error. But one ought rather to repent if he has done something against his own conscience, even though he recognizes later that he has done better than he thought he had.
Letter to Elisabeth, Oct. 6, 1645. IV, 307.
[Repentance] is a Christian virtue, which serves for the correction, not only of faults which are committed voluntarily, but also those which have been commited through ignorance, when some passion has prevented one from knowing the truth.
Letter to Elisabeth, Nov. 3, 1645. IV, 331.
Repentance is directly contrary to self-satisfaction; and it is a species of sadness which comes from the fact that one believes himself to have done some evil act; and it is very bitter, because its cause comes only from ourselves.
Passions, III, 191. XI, 472.
See satisfaction.
REPUTATION
I fear reputation more than I desire it, judging that it always manages to diminish the freedom and leisure of those who acquire it, and I have such perfect freedom and leisure, and value them so much, that there is no Monarch in the world who is rich enough to buy them from me.
Letter to Mersenne, Apr. 15, 1630. I, 136.
REST
The philosophers attribute to the smallest motion a condition which is much more solid and true than they do to rest, which they say is only a privation. As for me, I conceive that rest is a quality, which ought to be attributed to matter as long as it remains in one place, just as motion is a quality which is attributed to it when it changes place.
The World, VII. XI, 40.
I consider matter, left to itself and not receiving any impulse from elsewhere, as perfectly at rest.
Letter to More, Aug., 1649. V, 404.
REVELATION, DIVINE
Divine revelation gives us a certainty which is superior to every other kind of knowledge, since the faith that we give to it, even when it is obscure, is not an act of the intellect, but of the will.
Rules, III. X, 370.
RICH
A man who has only a thousand pistoles would be quite rich, if there were no other persons in the world who had more; and the same man would be quite poor, if there were no one in the world who did not have much more.
Letter to Chanut, June 6, 1647. V, 55.
RIDICULE
As for modest ridicule, which usefully reproves vice by making it appear ridiculous, yet without laughing at it, nor bearing witness to any hate against persons: this is not a passion, but a quality of a good man, which brings out his sense of humor, and the tranquility of his soul, which are marks of virtue; and often also the cleverness of his mind, insofar as he gives an amusing appearance to the things which he ridicules.
Passions, III, 180. XI, 465-466.
RING
In every motion there must be a circle or ring of bodies which move together.
Principles, II, 33. IX2, 81.
See vortex.
ROCKS
I do not know anything in particular concerning the generation of rocks, except that I distinguish them from metals, in that the tiny particles which make up the metals are notably larger than theirs.
Letter to Newcastle, Nov. 23, 1646. IV, 570.
RULES
The maxims of the sages can be reduced to a very small number of general rules.
Cogitationes Privatae. X, 217.
A large number of rules often shows the inexperience of the teacher, and if one can reduce them to a single, general precept, it is more concise than stating them as a large number of separate rules.
Rules, XVIII. X, 461.
RUMOR
[To Rumor:] You are so accustomed to lying when you precede us, that the wisest persons usually judge the truth to be the contrary of what you would have people believe.
Birth of Peace, XIV.