In place of references I have given in an appendix two short lists of easily accessible books which will give technical support to the substance of this little work. I have learnt much from them and taken—all but quoted—much. I make no apology for including, among books from which I have learnt, two of my own. Nothing teaches as solidly as trying to teach. And the record of a learner sometimes helps learners, when the oracles of the learned fail. But I must acknowledge here my own great indebtedness to two of those learned, my old instructors, Sir Edward Schäfer and Sir Edwin Ray Lankester, whose admirable lessons in the biological sciences of which they are distinguished professors laid a scientific foundation in me for all my subsequent study.
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The moon shines in my body, but my blind eyes cannot see it: The moon is within me, and so is the sun. The unstruck drum of Eternity is sounded within me; but my deaf ears cannot hear it. _Kabir._
Deep in every one of us there is a passion of desire to understand, just as there is of desire to enjoy and of desire to be somehow or other 'in the right.' I say deep in us, because we are in the habit either of burying these desires beneath a pretence of satisfying them or else of diverting our attention from them and thus letting them sink out of sight. So we live our life in the pursuit of other ends than those likely to be reached through understanding and rapture and righteousness. We falsify ourselves and our desires; yet unless we ruin the life within us they persist, waiting their hour.
There are moments when it becomes almost impossible for any man who has seen something of the marvel of every-day affairs to believe that he might spend time in vain if he were to try to convince his next-door neighbour that there was anything hard to understand about the crooking of a finger. Yet that is his experience when he tries. Just because every man who has a healthy finger in a healthy body and a healthy mind can and does crook it, there is nothing to wonder at. The whole affair is plain; it is familiar, happens every day. Familiarity lulls to sleep both the desire for understanding, and the sense of not understanding.