Passages about knowledge and truth

Tell me, O Muse, of that ingenious hero who travelled far and wide after he had sacked the famous town of Troy.

I would rather be a paid servant in a poor man's house and be above ground than king of kings among the dead.

Thou hast made us for Thyself, and our heart is restless, until it repose in Thee.

Give me chastity and continency, only not yet.

The unexamined life is not worth living for a human being.

I am very conscious that I am not wise at all; what then does the god mean?

I proclaim that justice is nothing else than the interest of the stronger.

Glaucon imagines a ring that makes its wearer invisible and asks whether any man, just or unjust, would keep his hands off what he wanted.

This proposition, I am, I exist, is necessarily true each time it is expressed by me, or conceived in my mind.

Some malignant demon, who is at once exceedingly potent and deceitful, has employed all his artifice to deceive me.

Count no man happy till he dies, free of pain at last.

Tiresias tells Oedipus that his wisdom is dreadful when it brings its possessor no profit, and refuses at first to say what he knows.

Crito, I owe a cock to Asclepius; will you remember to pay the debt?

I deem that the true votary of philosophy is likely to be misunderstood by other men; they do not perceive that he is always pursuing death and dying.

The desire and pursuit of the whole is what we call love.

Love is not a god and not a mortal, but something in between, a spirit born of Poverty and Resource, always needy, always scheming, never rich and never destitute.

Such evil deeds could religion prompt.

Nothing can ever be begotten of nothing by divine will.

The existence of God can be proved in five ways.

Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.

What do I know?

There is no desire more natural than that of knowledge.

In a village of La Mancha, the name of which I have no desire to call to mind, there lived not long since one of those gentlemen that keep a lance in the lance-rack, an old buckler, a lean hack, and a greyhound for coursing.

Sancho points out that the giants are windmills, and Quixote answers that the enchanter Freston turned them into windmills to rob him of the glory of the victory.

The eternal silence of these infinite spaces terrifies me.

The heart has its reasons, which reason does not know.

Nature is a source or cause of being moved and of being at rest in that to which it belongs primarily, in virtue of itself and not in virtue of a concomitant attribute.

Motion is the fulfilment of what exists potentially, in so far as it exists potentially.

Human knowledge and human power meet in one, for where the cause is not known the effect cannot be produced.

Nature to be commanded must be obeyed.

Good sense is, of all things among men, the most equally distributed; for every one thinks himself so abundantly provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a larger measure of this quality than they already possess.

I think, therefore I am, was so certain and of such evidence, that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it.

All the objects of human reason or enquiry may naturally be divided into two kinds, to wit, Relations of Ideas, and Matters of Fact.

Custom, then, is the great guide of human life.

Zwei Seelen wohnen, ach! in meiner Brust. Two souls, alas, dwell in my breast.

Verweile doch! du bist so schön! Stay a while! You are so beautiful!

A man cannot search either for what he knows or for what he does not know. He cannot search for what he knows, since he knows it, and in that case is in no need of searching; nor for what he does not know, for he does not know what to look for.

For seeking and learning are in fact nothing but recollection.

All men by nature desire to know.

There is a science which investigates being as being and the attributes which belong to this in virtue of its own nature.

I have not as yet been able to discover the reason for these properties of gravity from phenomena, and I do not feign hypotheses.

Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon.

I cannot but conclude the bulk of your natives to be the most pernicious race of little odious vermin that nature ever suffered to crawl upon the surface of the earth.

And he gave it for his opinion, that whoever could make two ears of corn or two blades of grass to grow upon a spot of ground where only one grew before, would deserve better of mankind, and do more essential service to his country, than the whole race of politicians put together.

Thoughts without content are empty, intuitions without concepts are blind.

Hitherto it has been assumed that all our knowledge must conform to objects. We must therefore make trial whether we may not have more success if we suppose that objects must conform to our knowledge.

The only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant.

If all mankind minus one were of one opinion, and only one person were of the contrary opinion, mankind would be no more justified in silencing that one person than he, if he had the power, would be justified in silencing mankind.

It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change.

Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, will tend to the preservation of that individual, and will generally be inherited by its offspring.

Supposing truth is a woman, what then?

He who fights with monsters should look to it that he himself does not become a monster. And if you gaze long into an abyss, the abyss also gazes into you.

I walk on air and contemplate the sun.

Zeus? What Zeus? There is no Zeus.

What is that which always is and has no becoming, and what is that which becomes and never is?

The father and maker of all this universe is past finding out; and even if we found him, to tell of him to all men would be impossible.

The soul is the first actuality of a natural body which has life potentially in it.

If the eye were an animal, sight would have been its soul.

A syllogism is discourse in which, certain things being stated, something other than what is stated follows of necessity from their being so.

We think we understand a thing without qualification when we think we know the cause on account of which it is so, and that it cannot be otherwise.

A point is that which has no part.

Let the following be postulated: to draw a straight line from any point to any point.

Withdraw into yourself and look. And if you do not find yourself beautiful yet, act as does the creator of a statue that is to be made beautiful: he cuts away here, he smooths there, until a lovely face has grown upon his work.

Never did eye see the sun unless it had first become sunlike.

I do not seek to understand that I may believe, but I believe in order to understand. For this also I believe, that unless I believed, I should not understand.

Even the fool is convinced that something than which nothing greater can be conceived exists at least in his understanding, since when he hears of this he understands it.

I began to think whether there might not be a motion, as it were, in a circle.

The heart of creatures is the foundation of life, the prince of all, the sun of their microcosm, on which all vegetation does depend, from whence all vigour and strength does flow.

The nature of an individual substance is to have a notion so complete that it is sufficient to comprehend and to allow the deduction of all the predicates of the subject to which the notion is attributed.

Every substance is like a complete world and like a mirror of God or of the whole universe, which each one expresses in its own way.

Their esse is percipi, nor is it possible they should have any existence out of the minds or thinking things which perceive them.

An idea can be like nothing but an idea.

The True is the whole.

Everything turns on grasping and expressing the True, not only as Substance, but equally as Subject.

Naked came I out of my mother's womb, and naked shall I return thither: the LORD gave, and the LORD hath taken away; blessed be the name of the LORD.

But where shall wisdom be found? and where is the place of understanding?

Life is short, the art long, opportunity fleeting, experiment perilous, and judgement difficult.

It is not, in my opinion, any more divine or more sacred than other diseases, but has a natural cause, and its supposed divine origin is due to men's inexperience and to their wonder at its peculiar character.

I know that I am mortal and the creature of a day; but when I search out the massed wheeling circles of the stars, my feet no longer touch the earth, but side by side with Zeus himself I take my fill of ambrosia.

It is our purpose to demonstrate for the five planets, as we did for the sun and moon, that all their apparent irregularities can be represented by uniform circular motions, since these alone are proper to the divine.

Nature does nothing in vain.

Each of the organs attracts the juice which is proper to it, as the lodestone attracts iron.

All instruction is either about things or about signs; but things are learnt by means of signs.

Whoever thinks that he understands the divine Scriptures or any part of them, but puts such an interpretation upon them as does not tend to build up this twofold love of God and our neighbour, does not yet understand them as he ought.

What part of life is not sorrowful and unpleasant, dull, insipid and troublesome, unless you add pleasure to it, that is to say, a seasoning of folly?

Now what else is the whole life of mortals but a sort of comedy, in which the various actors, disguised by various costumes and masks, walk on and play each one his part?

Our wisdom, in so far as it ought to be deemed true and solid wisdom, consists almost entirely of two parts: the knowledge of God and of ourselves.

Man's nature, so to speak, is a perpetual factory of idols.

In the middle of all sits the sun enthroned. In this most beautiful temple could we place this luminary in any better position from which he can illuminate the whole at once?

Mathematics is written for mathematicians.

The orbit of a planet is an ellipse, with the sun at one of the two foci.

A line joining a planet to the sun sweeps out equal areas in equal times.

The End of our Foundation is the knowledge of Causes, and secret motions of things; and the enlarging of the bounds of Human Empire, to the effecting of all things possible.

We have consultations, which of the inventions and experiences which we have discovered shall be published, and which not.

All the sciences are nothing other than human wisdom, which always remains one and the same, however different the subjects to which it is applied.

By a method I mean reliable rules which are easy to apply, such that whoever follows them exactly will never take what is false to be true, and will arrive at a true understanding of everything within his capacity.

Any problem in geometry can easily be reduced to such terms that a knowledge of the lengths of certain straight lines is sufficient for its construction.

Taking one line which I shall call unity in order to relate it as closely as possible to numbers, the product of two lines may be taken as a line.

The spaces described by a body falling from rest with a uniformly accelerated motion are to each other as the squares of the time intervals employed in traversing these distances.

If two stones of different weight are tied together, the slower should retard the faster and the faster hurry the slower, so that the pair moves more slowly than the heavier alone, and yet the pair is heavier than either.

As good almost kill a man as kill a good book: who kills a man kills a reasonable creature, God's image; but he who destroys a good book, kills reason itself, kills the image of God, as it were, in the eye.

I cannot praise a fugitive and cloistered virtue, unexercised and unbreathed, that never sallies out and sees her adversary.

By God I mean an absolutely infinite being, that is, substance consisting of infinite attributes, each of which expresses eternal and infinite essence.

Men believe themselves free because they are conscious of their volitions and their desire, and do not think, even in their dreams, of the causes by which they are disposed to want and to will.

Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas: how comes it to be furnished? To this I answer, in one word, from experience.

It is ambition enough to be employed as an under-labourer in clearing the ground a little, and removing some of the rubbish that lies in the way to knowledge.

My design in this book is not to explain the properties of light by hypotheses, but to propose and prove them by reason and experiments.

The light of the sun consists of rays differently refrangible.

The monad is nothing but a simple substance which enters into composites; simple, that is to say, without parts.

Monads have no windows through which anything could come in or go out.

Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.

Tis not contrary to reason to prefer the destruction of the whole world to the scratching of my finger.

Nothing is created, either in the operations of art or in those of nature, and it may be laid down as a principle that in every operation there is an equal quantity of matter before and after.

We cannot improve the language of any science without at the same time improving the science itself; neither can we, on the other hand, improve a science without improving the language which belongs to it.

I have at last succeeded in illuminating a magnetic curve or line of force, and in magnetising a ray of light.

Nothing is too wonderful to be true, if it be consistent with the laws of nature.

Can a historical point of departure be given for an eternal consciousness; how can such a point of departure be of more than historical interest; can an eternal happiness be built on historical knowledge?

The paradox is the passion of thought, and a thinker without a paradox is like a lover without passion: a mediocre fellow.

Call me Ishmael.

All visible objects, man, are but as pasteboard masks. If man will strike, strike through the mask! How can the prisoner reach outside except by thrusting through the wall?

The pragmatic method is primarily a method of settling metaphysical disputes that otherwise might be interminable. What difference would it practically make to anyone if this notion rather than that notion were true?

Theories thus become instruments, not answers to enigmas, in which we can rest.

The ego is not master in its own house.

A dream is a disguised fulfilment of a suppressed or repressed wish.

The things that are perish into the things out of which they come to be, according to necessity, for they pay penalty and retribution to each other for their injustice according to the ordering of time.

You cannot step twice into the same river, for other waters are ever flowing on.

Behold what I, a god, suffer at the hands of gods.

In one short word, learn the whole of it: every art that mortals have comes from Prometheus.

Is the pious loved by the gods because it is pious, or is it pious because it is loved by the gods?

I did not bid you tell me one or two of the many pious actions but that form itself that makes all pious actions pious.

If you associate with me, on the very day you will go home a better man, and the same the next day, and every day you will get better and better.

Zeus, fearing that our race would be wholly destroyed, sent Hermes to bring justice and shame to men, and ordered that all should have a share, for cities cannot exist if only a few share in them as in the other arts.

If someone should demonstrate that the likes themselves come to be unlike or the unlikes like, that, I think, would be a marvel; but if he shows that things which partake of both of these have both properties, there seems to me nothing strange about that.

You are still young, Socrates, and philosophy has not yet taken hold of you as I think it will. Then you will not despise even the meanest things.

My art of midwifery is in general like theirs; the only difference is that my patients are men, not women, and my concern is not with the body but with the soul that is in travail of birth.

Man is the measure of all things, of the things which are that they are, and of the things which are not that they are not.

Do not suppose that I am turning into a kind of parricide. We shall have to put the statement of father Parmenides to the torture, and insist that what is not, in some respect has being, and conversely that what is, in a way is not.

When we speak of what is not, it seems we do not mean something contrary to what is, but only something different from it.

Since we have to distinguish the causes and definitions of coming to be and passing away alike in all cases, and in the same way, we must treat also of growth and alteration.

The elements come to be out of one another reciprocally, and each has a pair of the qualities: fire is hot and dry, air hot and moist, water cold and moist, earth cold and dry.

We must not recoil with childish aversion from the examination of the humbler animals. Every realm of nature is marvellous.

If a man had been a work of art, we should not ask what he is made of but what he is for; and the same holds of the works of nature.

Give me a place to stand and I will move the earth.

The surface of any sphere is four times its greatest circle, and any cylinder having its base equal to the greatest circle of a sphere and height equal to the diameter is half as large again as the sphere.

Of the eight books, the first four form an elementary introduction. The first contains the modes of producing the three sections and the opposite branches, and their fundamental properties, worked out more fully and generally than in the writings of others.

The third book contains many remarkable theorems useful for the synthesis of solid loci, of which the most part and the most beautiful are new; and it was the discovery of these that made me aware that Euclid had not worked out the locus with respect to three and four lines.

In the beginning was the Word, and the Word was with God, and the Word was God. And the Word was made flesh, and dwelt among us.

For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.

All that has by nature with systematic method been arranged in the universe seems both in part and as a whole to have been determined and ordered in accordance with number, by the forethought and the mind of him that created all things.

Perfect numbers are equal to the sum of their own parts: six, twenty-eight, four hundred and ninety-six, eight thousand one hundred and twenty-eight.

Speech was instituted in order that we might either teach or be reminded. What then do we do when we speak, except teach or be taught?

If I am given a sign and I do not know the thing of which it is a sign, it teaches me nothing; if I know the thing, what does the sign teach me?

He began to wonder what it was that had left her, and where it had gone.

Everything that comes to be must have a cause, and the chain of causes cannot go on without end, so there must be a being whose existence is necessary.

All their life was spent not by laws, statutes or rules, but according to their own free will and pleasure. Their rule was this one clause: Do what you will.

I would rather have you learn nothing than learn such books under such masters, for their learning is but stupidity and their wisdom a sham, bastardising good and noble minds and spoiling the flower of youth.

In the discovery of hidden things and in the investigation of hidden causes, stronger reasons are obtained from sure experiments and demonstrated arguments than from probable conjectures and the opinions of philosophical speculators.

The terrella is a stone of magnetic substance ground into a sphere, and on it may be shown all the motions which the earth's own magnetic power produces in bodies placed upon it.

I have taken all knowledge to be my province.

They are ill discoverers that think there is no land, when they can see nothing but sea.