Rene Descartes
Sensations are nothing but confused modes of thinking.Collection: Confused
So blind is the curiosity by which mortals are possessed, that they often conduct their minds along unexplored routes, having no reason to hope for success, but merely being willing to risk the experiment of finding whether the truth they seek lies there.Collection: Lying
Thus each truth discovered was a rule available in the discovery of subsequent ones.Collection: Discovery
Because reason...is the only thing that makes us men, and distinguishes us from the beasts, I would prefer to believe that it exists, in its entirety, in each of us.Collection: Believe
Divide each difficulty at hand into as many pieces as possible and as could be required to better solve them.Collection: Hands
In philosophy, when we make use of false principles, we depart the farther from the knowledge of truth and wisdom exactly in proportion to the care with which we cultivate them, and apply ourselves to the deduction of diverse consequences from them, thinking that we are philosophizing well, while we are only departing the farther from the truth; from which it must be inferred that they who have learned the least of all that has been hitherto distinguished by the name of philosophy are the most fitted for the apprehension of truth.Collection: Philosophy
In the matter of a difficult question it is more likely that the truth should have been discovered by the few than by the many.Collection: Truth
The only secure knowledge is that I exist.Collection: Philosophical
The principal effect of the passions is that they incite and persuade the mind to will the events for which they prepared the body.Collection: Passion
If ... it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power, namely, suspend judgement.Collection: Judgement
Let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something.Collection: Thinking
Variant: When it is not in our power to follow what is true, we ought to follow what is most probable.Collection: Philosophical
Neither divine grace nor natural knowledge ever diminishes freedom.Collection: Grace
When I consider this carefully, I find not a single property which with certainty separates the waking state from the dream. How can you be certain that your whole life is not a dream?Collection: Love
There is nothing so far removed from us as to be beyond our reach, or so hidden that we cannot discover it.Collection: Persistence
I suppose therefore that all things I see are illusions; I believe that nothing has ever existed of everything my lying memory tells me. I think I have no senses. I believe that body, shape, extension, motion, location are functions. What is there then that can be taken as true? Perhaps only this one thing, that nothing at all is certain.Collection: Memories
The greatest minds, as they are capable of the highest excellencies, are open likewise to the greatest aberrations; and those who travel very slowly may yet make far greater progress, provided they keep always to the straight road, than those who, while they run, forsake it.Collection: Running
For I found myself embarrassed with so many doubts and errors that it seemed to me that the effort to instruct myself had no effect other than th eincreasing discovery of my own ignoranceCollection: Ignorance
How do we know that anything really exists, that anything is really the way it seems ot us through our senses?Collection: Way
Now therefore, that my mind is free from all cares, and that I have obtained for myself assured leisure in peaceful solitude, I shall apply myself seriously and freely to the general destruction of all my former opinions.Collection: Peaceful
These long chains of perfectly simple and easy reasonings by means of which geometers are accustomed to carry out their most difficult demonstrations had led me to fancy that everything that can fall under human knowledge forms a similar sequence; and that so long as we avoid accepting as true what is not so, and always preserve the right order of deduction of one thing from another, there can be nothing too remote to be reached in the end, or to well hidden to be discovered.Collection: Fall
Instead I ought to be grateful to Him who never owed me anything for having been so generous to me, rather than think that He deprived me of those things or has taken away from me whatever He did not give me.Collection: Taken
The principal use of prudence, of self-control, is that it teaches us to be masters of our passions, and to so control and guide them that the evils which they cause are quite bearable, and that we even derive joy from them all.Collection: Anger
The mind effortlessly and automatically takes in new ideas, which remain in limbo until verified or rejected by conscious, rational analysis.Collection: Ideas
... regard this body as a machine which, having been made by the hand of God, is incomparably better ordered than any machine that can be devised by man, and contains in itself movements more wonderful than those in any machine. ... it is for all practical purposes impossible for a machine to have enough organs to make it act in all the contingencies of life in the way in which our reason makes us act.Collection: Men
There is a great difference between mind and body insomuch as body is by nature always divisible, and the mind is entirely indivisible.Collection: Differences
The entire method consists in the order and arrangement of the things to which the mind's eye must turn so that we can discover some truth.Collection: Eye
Here I beg you to observe in passing that the scruples that prevented ancient writers from using arithmetical terms in geometry, and which can only be a consequence of their inability to perceive clearly the relation between these two subjects, introduced much obscurity and confusion into their explanations.Collection: Two
It must not be thought that it is ever possible to reach the interior earth by any perseverance in mining: both because the exterior earth is too thick, in comparison with human strength; and especially because of the intermediate waters, which would gush forth with greater impetus, the deeper the place in which their veins were first opened; and which would drown all miners.Collection: Perseverance
The nature of matter, or body considered in general, consists not in its being something which is hard or heavy or coloured, or which affects the senses in any way, but simply in its being something which is extended in length, breadth and depth.Collection: Science
I concluded that I might take as a general rule the principle that all things which we very clearly and obviously conceive are true: only observing, however, that there is some difficulty in rightly determining the objects which we distinctly conceive.Collection: Math
If we possessed a thorough knowledge of all the parts of the seed of any animal (e.g. man), we could from that alone, be reasons entirely mathematical and certain, deduce the whole conformation and figure of each of its members, and, conversely if we knew several peculiarities of this conformation, we would from those deduce the nature of its seed.Collection: Nature
Archimedes, that he might transport the entire globe ... demanded only a point that was firm and immovable; so also, I shall be entitled to entertain the highest expectations, if I am fortunate enough to discover only one thing that is certain and indubitable.Collection: Expectations
There is a difference between happiness, the supreme good, and the final end or goal toward which our actions ought to tend. For happiness is not the supreme good, but presupposes it, being the contentment or satisfaction of the mind which results from possessing it.Collection: Differences
This result could have been achieved either by his [God] endowing my intellect with a clear and distinct perception of everything about which I would ever deliberate, or simply by impressing the following rule so firmly upon my memory that I could never forget it: I should never judge anything that I do not clearly and distinctly understand.Collection: Memories
Good sense is the most equitably distributed of all things because no matter how much or little a person has, everyone feels so abundantly provided with good sense that he feels no desire for more than he already possesses.Collection: Desire
There is a little gland in the brain in which the soul exercises its functions in a more particular way than in the other parts.Collection: Exercise
As I considered the matter carefully it gradually came to light that all those matters only were referred to mathematics in which order and measurements are investigated, and that it makes no difference whether it be in numbers, figures, stars, sounds or any other object that the question of measurement arises. I saw consequently that there must be some general science to explain that element as a whole which gives rise to problems about order and measurement, restricted as these are to no special subject matter. This, I perceived was called 'universal mathematics'.Collection: Stars
Human wisdom remains always one and the same although applied to the most diverse objects and it is no more changed by their diversity than the sunshine is changed by the variety of objects which it illuminates.Collection: Sunshine
I experienced in myself a certain capacity for judging which I have doubtless received from God, like all the other things that I possess; and as He could not desire to deceive me, it is clear that He has not given me a faculty that will lead me to err if I use it aright.Collection: Judging
For how do we know that the thoughts which occur in dreaming are false rather than those others which we experience when awake, since the former are often not less vivid and distinct than the latter?Collection: Dream
It is contrary to reasoning to say that there is a vacuum or space in which there is absolutely nothing.Collection: Space
Everybody thinks himself so well supplied with common sense that even those most difficult to please. . . never desire more of it than they already have.Collection: Thinking
And thereby make ourselves, as it were, the lords and masters of nature.Collection: Science
If I go for the alternative which is false, then obviously I shall be in error; if I take the other side, then it is by... chance that I arrive at the truth, and I shall still be at fault.... In this incorrect use of free will may be found the privation which constitutes the essence of error.Collection: Essence
... moral certainty is certainty which is sufficient to regulate our behaviour, or which measures up to the certainty we have on matters relating to the conduct of life which we never normally doubt, though we know that it is possible, absolutely speaking, that they may be false.Collection: Doubt
Even if I were to suppose that I was dreaming and whatever I saw or imagined was false, yet I could not deny that ideas were truly in my mind.Collection: Dream
[About Pierre de Fermat] It cannot be denied that he has had many exceptional ideas, and that he is a highly intelligent man. For my part, however, I have always been taught to take a broad overview of things, in order to be able to deduce from them general rules, which might be applicable elsewhere.Collection: Science
I should consider that I know nothing about physics if I were able to explain only how things might be, and were unable to demonstrate that they could not be otherwise.Collection: Science