I can doubt everything, except one thing, and that is the very fact that I doubt. Simply put–I think, therefore I am — Rene Descartes

Dubium sapientiae initium. (Doubt is the origin of wisdom.) — René Descartes

Dubito, ergo cogito, ergo sum. (English: ‘I doubt, therefore I think, therefore I am’) — René Descartes

If you would be a real seeker after truth, it is necessary that at least once in your lIfe you doubt, as far as possible, all things. — Rene Descartes

The first precept was never to accept a thing as true until I knew it as such without a single doubt. — Rene Descartes

I am thing that thinks: that is, a things that doubts,affirms, denies, understands a few things, is ignorant of many things, is willing, is unwilling, and also which imagines and has sensory perceptions. — Rene Descartes

All is to be doubted. — Rene Descartes

I know that I exist; the question is, What is this ‘I’ that ‘I’ know. — Rene Descartes

When it is not in our power to follow what is true, we ought to follow what is most probable. — Rene Descartes

Variant: When it is not in our power to follow what is true, we ought to follow what is most probable. — Rene Descartes

For each of us there is a set limit to our intellectual powers which we cannot pass. — Rene Descartes

Except our own thoughts, there is nothing absolutely in our power. — Rene Descartes

The only thing we have power over in the universe is our own thoughts. — Rene Descartes

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. — Rene Descartes

Science is practical philosophy. — Rene Descartes

I know not If I was then a man dreamIng I was a butterfly, or If I am now a butterfly dreamIng I am a man. — Rene Descartes

It is possible that I am dreaming right now and that all of my perceptions are false. — Rene Descartes

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? — Rene Descartes

Reason is nothing without imagination. — Rene Descartes

How can you be certain that your whole life is not a dream? — Rene Descartes

I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake. — Rene Descartes

The only secure knowledge is that I exist. — Rene Descartes

I was convinced that our beliefs are based much more on custom and example than on any certain knowledge. — Rene Descartes

Neither divine grace nor natural knowledge ever diminishes freedom. — Rene Descartes

The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge. — Rene Descartes

Mathematics is a more powerful instrument of knowledge than any other that has been bequeathed to us by human agency. — Rene Descartes

Intuitive knowledge is an illumination of the soul, whereby it beholds in the light of God those things which it pleases Him to reveal to us by a direct impression of divine clearness. — Rene Descartes

There is nothing more ancient than the truth. — Rene Descartes

Few look for truth; many prowl about for a reputation of profundity by arrogantly challenging whichever arguments are the best. — Rene Descartes

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. — Rene Descartes

Thus each truth discovered was a rule available in the discovery of subsequent ones. — Rene Descartes

To live without philosophizing is in truth the same as keeping the eyes closed without attempting to open them. — Rene Descartes

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. — Rene Descartes

If I simply refrain from making a judgment in cases where I do not perceive the truth with sufficient clarity and distinctness, then it is clear that I am behaving correctly and avoiding error. — Rene Descartes

It is not enough to have a good mind; the main thing is to use it well. — Rene Descartes

The greatest minds are capable of the greatest vices as well as of the greatest virtues. — René Descartes

For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it. — Rene Descartes

I am indeed amazed when I consider how weak my mind is and how prone to error. — Rene Descartes

The mind effortlessly and automatically takes in new ideas, which remain in limbo until verified or rejected by conscious, rational analysis. — Rene Descartes

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. — Rene Descartes

In order to improve the mind, we ought less to learn, than to contemplate. — Rene Descartes

Intuition is the undoubting conception of a pure and attentive mind, which arises from the light of reason alone, and is more certain than deduction. — Rene Descartes

But in my opinion, all things in nature occur mathematically. — Rene Descartes

At last I will devote myself sincerely and without reservation to the general demolition of my opinions. — Rene Descartes

It is certain that I am really distinct from my body, and can exist without it. — Rene Descartes

There is a great difference between mind and body insomuch as body is by nature always divisible, and the mind is entirely indivisible. — Rene Descartes

It is to the body alone that we should attribute everything that can be observed in us to oppose our reason. — Rene Descartes

The principal effect of the passions is that they incite and persuade the mind to will the events for which they prepared the body. — Rene Descartes