Tractatus Logico-Philosophicus

If I cannot say a priori what elementary propositions there are, then the attempt to do so must lead to obvious nonsense.

A tautology's truth is certain, a 's possible, a contradiction's impossible. (Certain, possible, impossible: here we have the first indication of the scale that we need in the theory of probability.)

The world and life are one.

Propositions are truth-functions of elementary propositions. (An elementary proposition is a truth-function of itself.)

Whereof one cannot speak, thereof one must be silent.

Philosophy aims at the logical clarification of thoughts. Philosophy is not a body of doctrine but an activity. A philosophical work consists essentially of elucidations. Philosophy does not result in 'philosophical propositions', but rather in the clarification of propositions. Without philosophy thoughts are, as it were, cloudy and indistinct: its task is to make them clear and to give them sharp boundaries.

The subject does not belong to the world, but it is a limit of the world.

The limits of my language mean the limits of my world.

The world of the happy is quite different from the world of the unhappy.

It is quite impossible for a proposition to state that it itself is true.

The thought is the significant proposition.

There are, indeed, things that cannot be put into words. They make themselves manifest. They are what is mystical.

Though a state of affairs that would contravene the laws of physics can be represented by us spatially, one that would contravene the laws of geometry cannot.

Death is not an event in life: we do not live to experience death. If we take eternity to mean not infinite temporal duration but timelessness, then eternal life belongs to those who live in the present. Our life has no end in just the way in which our visual field has no limits.

Logic pervades the world: the limits of the world are also its limits. So we cannot say in logic, "The world has this in it, and this, but not that." For that would appear to presuppose that we were excluding certain possibilities, and this cannot be the case, since it would require that logic should go beyond the limits of the world; for only in that way could it view those limits from the other side as well. We cannot think what we cannot think; so what we cannot think we cannot say either.

I am my world. (The microcosm.)

The logical picture of the facts is the thought.

My propositions are elucidatory in this way: he who understands me finally recognizes them as senseless, when he has climbed out through them, on them, over them. (He must so to speak throw away the ladder, after he has climbed up on it.)

The whole sense of the book might be summed up the following words: what can be said at all can be said clearly, and what we cannot talk about we must pass over in silence.

The world is the totality of facts, not things.

The world is all that is the case.

What is the case, the fact, is the existence of atomic facts.

Scepticism is not irrefutable, but obviously nonsensical, when it tries to raise doubts where no questions can be asked.

For doubt can exist only where a question exists, a question only where an answer exists, and an answer only where something can be said.

Nicht wie die Welt ist, ist das Mystische, sondern dass sie ist.

This remark provides the key to the problem, how much truth there is in solipsism. For what the solipsist means is quite correct; only it cannot be said, but makes itself manifest. The world is my world: this is manifest in the fact that the limits of language (of that language which alone I understand) mean the limits of my world.

It is not how things are in the world that is mystical, but that it exists.

The aim of the book is to set a limit to thought, or rather — not to thought, but to the expression of thoughts: for in order to be able to set a limit to thought, we should have to find both sides of the limit thinkable (i.e. we should have to be able to think what cannot be thought).

It will therefore only be in language that the limit can be set, and what lies on the other side of the limit will simply be nonsense.