Ordinarily we communicate intelligence to each other by speech. I first call up in my own brain a picture of a scene I wish to describe, and then, by… - William Crookes

It has been said that "Nothing worth the proving can be proved, nor yet disproved." True though this may have been in the past, it is true no longer. The science of our century has forged weapons of observation and analysis by which the veriest tyro may profit. Science has trained and fashioned the average mind into habits of exactitude and disciplined perception, and in so doing has fortified itself for tasks higher, wider, and incomparably more wonderful than even the wisest among our ancestors imagined. Like the souls in Plato's myth that follow the chariot of Zeus, it has ascended to a point of vision far above the earth. It is henceforth open to science to transcend all we now think we know of matter and to gain new glimpses of a profounder scheme of Cosmic law.

If a possible — nay, reasonable — variation in only one of the forces conditioning the human race, that of gravitation, could so modify our outward form, appearance, and proportions as to make us to all intents and purposes a different race of beings; if mere differences of size can cause some of the most simple facts in chemistry and physics to take so widely different a guise; if beings microscopically small and prodigiously large would simply as such be subject to the hallucinations I have pointed out, and to others I might enlarge upon, is it not possible that we, in turn, though occupying, as it seems to us, the golden mean, may also by the mere virtue of our size and weight fall into misinterpretations of phenomena from which we should escape were we or the globe we inhabit either larger or smaller, heavier or lighter? May not our boasted knowledge be simply conditioned by accidental environments, and thus be liable to a large element of subjectivity hitherto unsuspected and scarcely possible to eliminate?

I am not disposed to bewail the limitations imposed by human ignorance. On the contrary, I feel ignorance is a healthful stimulant; and my enforced conviction that neither I nor anyone can possibly lay down beforehand what does not exist in the universe, or even what is not going on all round us everyday of our lives, leaves me with a cheerful hope that something very new and very arresting may turn up anywhere at any minute. … I shall try to utilize this temper of mind today by clearing away, so far as I can, certain presuppositions, on one side or on the other, which seem to me to depend upon a too hasty assumption that we know more about the universe than as yet we really can know.