The special theory of relativity... creates a formal dependence between the way in which the spatial co-ordinates on the one hand, and the temporal co-ordinates, on the other, have to enter into the natural laws.

I hold the relay race theory of history: progress in human affairs depends upon accepting, generation after generation, the individual duty to oppose the evils of the time.

A current time-slice theory makes the justificational status of a belief wholly a function of what is true of the cognizer at the time of belief. An historical theory makes the justificational status of a belief depend on its prior history. Since my historical theory emphasizes the reliability of the belief-generating processes, it may be called ‘historical reliabilism.’

Nothing whatever can be said in support of the assumption that nature will usually follow the simpler theory... The simplest theory is to be chosen not because it is most likely to be true but because it is scientifically the most rewarding among equally likely alternatives. We aim at simplicity and hope for truth.

There is a distinction, but no opposition, between theory and practice. Each to a certain extent supposes the other. Theory is dependent on practice; practice must have preceded theory.

The outstanding achievement of twentieth-century physics is not the theory of relativity with its welding together of space and time, or the theory of quanta with its present apparent negation of the laws of causation, or the dissection of the atom with the resultant discovery that things are not what they seem; it is the general recognition that we are not yet in contact with the ultimate reality. We are still imprisoned in our cave, with our backs to the light, and can only watch the shadows on the wall.

The theory of Communism may be summed up in one sentence: Abolish all private property.

High theory and mere mind-stimulation are secondary; living itself - in the real world, among people - is the essence... I hereby promise to attempt to be a mensh, a decent, caring human being. Neutrality, noncommitment, indifference have no place in life. To be fully human, we are committed to being caring, sensitive, aggressively compassionate people. Our lives are defined by how we act. We are alive because we perform just and righteous deeds, deeds of gentle loving kindness.

It is better to emit a scream in the shape of a theory than to be entirely insensible to the jars and incongruities of life and take everything as it comes in a forlorn stupidity.

The theory that can absorb the greatest number of facts, and persist in doing so, generation after generation, through all changes of opinion and of detail, is the one that must rule all observation.

The whole theory of the universe is directed unerringly to one single individual - namely to You.

There runs throughout Nature unmistakable evidence of thought, corresponding to the mental operations of our own mind, and therefore intelligible to us as thinking beings, and unaccountable on any other basis than that they owe their existence to the working of intelligence; and no theory that overlooks this element can be true to nature.

The ancient theory of the just war breaks down when victory is impossible, when the weapons are so undiscriminating as to destroy both sides.

Everything on the earth has a purpose, every disease an herb to cure it, and every person a mission. This is the Indian theory of existence.

Agnosticism denies to the human mind a power of attaining knowledge which it does possess... Agnosticism, as such, is a theory about knowledge and not about religion.

Moral ambiguity creates mental cramps of various sorts, which lead to reflection, discussion, and argument… Morality resists theoretical unification under either a set of special-purpose rules or single general-purpose rule or principle, such as the categorical imperative or the principle of unity. If this is right, and if it is right because the ends of moral life are plural and heterogeneous in kind and because our practices of moral education rightly reflect this, then we have some greater purchase on why the project of finding a single theoretically satisfying moral theory has failed.

Three claims: (1) Consciousness exists. There exist conscious mental states, events, and processes that have the property of being conscious. (2) Consciousness has depth, hidden structure, hidden and possibly multiple functions, and hidden natural and cultural history. Conscious mental states supervene on brain states. (3) Conscious mental states, processes, events – possibly conscious supervisory faculties, if there are any – are heterogeneous in phenomenal world. A theory of consciousness will in the end be part of a unified theory of the mind.

The doctrine that the will alone is the way to power is a most woe-begone theory for the relief to the morally sick.

Today scientists describe the universe in terms of two basic partial theories – the general theory of relativity and quantum mechanics. They are the great intellectual achievements of this century. The general theory of relativity describes the force of gravity and the large-scale structure of the universe (that is the structure on scales from only a few miles to as large as a million million million million miles – the size of the observable universe). Quantum mechanics, on the other hand, deals with phenomena on extremely small scales, such as a millionth of a millionth of an inch. Unfortunately, however, these two theories are known to be inconsistent with each other – they cannot both be correct.

If we do discover a complete [unified] theory [of the universe], it should be in time be understandable in broad principle by everyone, not just a few scientists. Then we shall all, philosophers, scientists, and just ordinary people, be able to take part in the discussion of the question of why it is that we and the universe exist. If we find the answer to that, it would be the ultimate triumph of human reason – for then we should know the mind of God.