Something unknown is doing we don't know what-that is what our theory amounts to.

We often think that when we have completed our study of one we know all about two, because 'two' is 'one and one.' We forget that we still have to make a study of 'and.'

If I let my fingers wander idly over the keys of a typewriter it might happen that my screed made an intelligible sentence. If an army of monkeys were strumming on typewriters they might write all the books in the British Museum. The chance of their doing so is decidedly more favourable than the chance of the molecules returning to one half of the vessel.

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.

A hundred thousand million Stars make one Galaxy; A hundred thousand million Galaxies make one Universe. The figures may not be very trustworthy, but I think they give a correct impression.

For the truth of the conclusions of physical science, observation is the supreme Court of Appeal.

The mathematics is not there till we put it there.