We used to think that if we knew one, we knew two, because one and one are two. We are finding that we must learn a great deal more about 'and'.

Electrical force is defined as something which causes motion of electrical charge; an electrical charge is something which exerts electric force.

There is only one law of Nature-the second law of thermodynamics-which recognises a distinction between past and future more profound than the difference of plus and minus. It stands aloof from all the rest. ... It opens up a new province of knowledge, namely, the study of organisation; and it is in connection with organisation that a direction of time-flow and a distinction between doing and undoing appears for the first time.

Let us suppose that an ichthyologist is exploring the life of the ocean. He casts a net into the water and brings up a fishy assortment. Surveying his catch, he proceeds in the usual manner of a scientist to systematise what it reveals. He arrives at two generalisations: No sea-creature is less than two inches long. (2) All sea-creatures have gills. These are both true of his catch, and he assumes tentatively that they will remain true however often he repeats it.

So far as physics is concerned, time's arrow is a property of entropy alone.

Science is one thing, wisdom is another. Science is an edged tool, with which men play like children, and cut their own fingers.

An ocean traveler has even more vividly the impression that the ocean is made of waves than that it is made of water.