Not till we know the law of ourselves, in fact, shall we know the law of the emerald and the orange, or of Nature generally; and the law of ourselves is not learnt, except subordinately, by intellectual investigation; it is mainly learnt by life. The relation of gravity to vitality is learnt not so much by outer experiment in a laboratory as by long experience within ourselves from the day when as infants we cannot lift ourselves above the floor, through the years of the proud strength of manhood scaling the loftiest mountains, to the hour when our disengaged spirits finally overcome and pass beyond the attraction of the earth; and just as the sense of weight--which first appears as a quite external sensation--is thus at last found to stand in most pregnant relation with our deepest selves, so of the other senses which feed the individual life--the senses of light, of warmth, of taste, of sound, of smell. Taste, which begins as it were on the tip of the tongue, becomes ultimately, if normally developed, a sense which identifies itself with the health and well-being of the whole body; the pleasure of taste becomes vastly more than a mere surface pleasure, and its discrimination of food more than a mere regard for the nutrition of the ordinary corporeal functions. The sense of Light, which begins in the material eye, grows and deepens inwardly till the consciousness of it pervades the whole body and mind with a kind of inward illumination or divine Reason, showing the places of all things and enfolding the sense of beauty in itself. The sense of Warmth in the same manner is related to and leads up to Love; and Sound, in the voices of our friends or the divine chords of music, has passed away from being an external phenomenon and has established itself as the language of our most tender and intimate emotions.