Gottlob Frege created modern logic including "for all," "there exists," and rules of proof. Leibniz and Boole had dealt only with what we now call "propositional logic" (that is, no "for all" or "there exists"). They also did not concern themselves with rules of proof, since their aim was to reach truth by pure calculation with symbols for the propositions. Frege took the opposite track: instead of trying to reduce logic to calculation, he tried to reduce mathematics to logic, including the concept of number.

I, however, place economy among the first and most important republican virtues, and public debt as the greatest of the dangers to be feared.

The cause of anger is the belief that we are injured; this belief, therefore, should not be lightly entertained. We ought not to fly into a rage even when the injury appears to be open and distinct: for some false things bear the semblance of truth. We should always allow some time to elapse, for time discloses the truth.

The Process of Induction may be resolved into three steps ; the 'Selection of the Idea', the 'Construction of the Conception', and the 'Determination of the Magnitudes'. These three steps correspond to the determination of the 'Independent Variable', the 'formula', and the 'coefficients', in mathematical investigations; or to the 'Argument', the 'Law', and the 'Numerical Data', in a Table of an Inequality. The conceptions involved in scientific truths have attained the requisite degree of clearness by means of the Discussions respecting ideas which have taken place among discoverers and their followers. Such discussions are very far from being unprofitable

What, by a word lacking even in grammar, is called amorality, is a thing that does not exist. If you are unwilling to submit to any norm, you have, nolens volens, to submit to the norm of denying all morality, and this is not amoral, but immoral. It is a negative morality which preserves the empty form of the other.

Necessity, as well as patriotism and confidence, will make us all eager to receive treasury notes, if founded on specific taxes. Congress may borrow of the public, and without interest, all the money they may want, to the amount of a competent circulation, by merely issuing their own promissory notes, of proper denominations for the larger purposes of circulation, but not for the small. Leave that door open for the entrance of metallic money.

There is no connection between the elements in an electric world, which is equivalent to being surrounded by the human unconscious.

Unlike previous environmental changes, the electric media constitutes a total and near-instanteous transformation of culture, values and attitudes.

Taken as a whole, the Cross Correspondences and the Willet scripts are among the most convincing evidence that at present exists for life after death. For anyone who is prepared to devote weeks to studying them, they prove beyond all reasonable doubt that Myers, Gurney, and Sidgwick went on communicating after death.

Those that will combat use and custom by the strict rules of grammar do but jest.

The inclination to act as the laws command, a virtue, is a synthesis in which the law ... loses its universality and the subject its particularity; both lose their opposition, while in the Kantian conception of virtue this opposition remains, and the universal becomes the master and the particular the mastered.

None of the things they learn, should ever be made a burthen to them, or impos's on them as a task. Whatever is so proposed, presently becomes irksome; the mind takes an aversion to it, though before it were a thing of delight or indifferency. Let a child but be ordered to whip his top at a certain time every day, whether he has or has not a mind to it; let this be but requir'd of him as a duty, wherein he must spend so many hours morning and afternoon, and see whether he will not soon be weary of any play at this rate. Is it not so with grown men?

The mob has always behaved in this way-eagerly open to bribes that cannot be honorably accepted, and dissolutely callous to degradation and insult that cannot be honorably endured.

The evil of marriage, as is it practiced in the European countries, extends further than we have yet described. The method is for a thoughtless and romantic youth of each sex, to come together, to see each other, for a few times, and under circumstances full of delusion and then to vow eternal attachment. What is the consequence of this? In almost every instance they find themselves deceived. They are reduced to make the best of an irretrievable mistake. They are led to conceive it their wiser policy, to shut their eyes upon realities, happy, if by any perversion of intellect, they can persuade themselves that they were right in their first crude opinion of each other. Thus the institution of marriage is made a system of fraud; and men who carefully mislead their judgement in the daily affair of their life, must be expected to have a crippled judgement in every other concern.

For a people who are free, and who mean to remain so, a well organized and armed militia is their best security.

Freedom is the greatest of political goods. I do not say freedom is the greatest of all goods: the best things come from within-they are such things as creative art, and love, and thought. Such things can be helped or hindered by political conditions, but not actually produced by them; and freedom is, both in itself and in its relation to these other goods the best thing that political and economic conditions can secure.

It is terrible to see how a single unclear idea, a single formula without meaning, lurking in a young man's head, will sometimes act like an obstruction ... in an artery, hindering the nutrition of the brain, and condemning its victim to pine away in the fullness of his intellectual vigor and in the midst of intellectual plenty.

No doubt you know that Galileo had been convicted not long ago by the Inquisition, and that his opinion on the movement of the Earth had been condemned as heresy. Now I will tell you that all things I explain in my treatise, among which is also that same opinion about the movement of the Earth, all depend on one another, and are based upon certain evident truths. Nevertheless, I will not for the world stand up against the authority of the Church. ...I have the desire to live in peace and to continue on the road on which I have started.

And O! how the mind is here washed clean of all its early ingrafted Jewish superstition ! It is the most profitable and elevating reading which is possible in the world. It has been the solace of my life, and will be the solace of my death.

The much occupied man has no time for wantonness, and it is an obvious commonplace that the evils of leisure can be shaken off by hard work.

Being is continuous becoming.

For what is lacking now is not quibbles; nay, the books of the Stoics are full of quibbles.

This happy state can only be obtained by a prudent care of the body, and a steady government of the mind. The diseases of the body are to be prevented by temperance, or cured by medicine, or rendered tolerable by patience.

Not from a vain or shallow thought His awful Jove young Phidias brought.

I do not speak here of divine truths... because they are infinitely superior to nature: God alone can place them in the soul... I know that he has desired that they should enter from the heart into the mind, and not from the mind into the heart, to humiliate that proud power of reasoning that pretends to the right to be the judge of the things that the will chooses; and to cure this infirm will which is wholly corrupted by its filthy attachments.

Don't think money does everything or you are going to end up doing everything for money.

Man works when he is partially involved. When he is totally involved he is at play or leisure.

I am more and more convinced that poetry is the universal possession of mankind, revealing itself everywhere and at all times in hundreds and hundreds of men. ... I therefore like to look about me in foreign nations, and advise everyone to do the same. National literature is now a rather unmeaning term; the epoch of world literature is at hand, and everyone must strive to hasten its approach.

As to the viciousness of the philosophers, the meaning of this complaint is succinctly expressed in the charge that the philosophers do not "hold the gods the city holds." And this accusation is most true. The quest for wisdom begins in doubt of the conventional wisdom about the highest things. The most cherished beliefs of the community, the collective hopes and fears, are centered on its gods. The unpardonable thing is to be beyond these hopes and fears, beyond the awe and shame the gods impose.

Answers determined by the social division of labor become truth as such.

And why be scandalized by the infallibility of a man, of the Pope? What difference does it make whether it be a book that is infallible - the Bible, or a society of men - the Church, or a single man? Does it make any essential change in the rational difficulty? And since the infallibility of a book or of a society of men is not more rational than that of a single man, this supreme offense to the eyes of reason has to be postulated.

When alterations in technical terms become necessary, it is desirable that the new term should contain in its form some memorial of the old one.

The best doctor is the one you run for and can't find.

Our laws, language, religion, politics, & manners are so deeply laid in English foundations, that we shall never cease to consider their history as a part of ours, and to study ours in that as it's origin.

Neither perception nor true opinion, nor reason or explanation combined with true opinion could be knowledge. Then our art of midwifery declare to us that all the offspring that have been born are mere wind-eggs and not worth rearing and if you remain barren, you will be less harsh and gentler to your associates, for you will have the wisdom not to think you know that which you do not know.

I do not accept any absolute formulas for living. No preconceived code can see ahead to everything that can happen in a man's life. As we live, we grow and our beliefs change. They must change. So I think we should live with this constant discovery. We should be open to this adventure in heightened awareness of living. We should stake our whole existence on our willingness to explore and experience.

And since these things are so, we must suppose that there are contained many things and of all sorts in the things that are uniting, seeds of all things, with all sorts of shapes and colours and savours.

The terrifying experience and obsession of death, when preserved in consciousness, becomes ruinous. If you talk about death, you save part of yourself. But at the same time, something of your real self dies, because objectified meanings lose the actuality they have in consciousness.

In all ages of the world, priests have been enemies to liberty; and it is certain, that this steady conduct of theirs must have been founded on fixed reasons of interest and ambition. Liberty of thinking, and of expressing our thoughts, is always fatal to priestly power, and to those pious frauds, on which it is commonly founded; and, by an infallible connexion, which prevails among all kinds of liberty, this privilege can never be enjoyed, at least has never yet been enjoyed, but in a free government.

In the empire of signs, the soul, psychology, is erased. There is no soul to infect the holy seriousness of ritual play.

It would be better for me that multitudes of men should disagree with me rather than that I, being one, should be out of harmony with myself.

The first act of violence that patriarchy demands of males is not violence toward women. Instead patriarchy demands of all males that they engage in acts of psychic self-mutilation, that they kill off the emotional parts of themselves. If an individual is not successful in emotionally crippling himself, he can count on patriarchal men to enact rituals of power that will assault his self-esteem.

Death makes no sense except to people who have passionately loved life. How can one die without having something to part from? Detachment is a negation of both life and death. Whoever has overcome his fear of death has also triumphed over life. For life is nothing but another word for this fear.

We must plan for freedom, and not only for security, if for no other reason than that only freedom can make security secure.

The unfortunate thing about public misfortunes is that everyone regards himself as qualified to talk about them.

Pain he endures, death he awaits.

Science may set limits to knowledge, but should not set limits to imagination.

See thou tell no man; but go thy way, shew thyself to the priest, and offer the gift that Moses commanded, for a testimony unto them.

It is a very helpful insight to say we are vehicles for our DNA, we are hosts for DNA parasites which are our genes. Those are insights which help us to understand an aspect of life. But it's emotive to say, that's all there is to it, we might as well give up going to Shakespeare plays and give up listening to music and things, because that's got nothing to do with it. That's an entirely different subject.