APPENDIX
MATHEMATICAL AND PHYSICAL NOTIONS[342]
Infinity and the notion of the limit. Functionality. Frequency distributions and probability. Matter, force, mass, and inertia. Energy-transformations. Isothermal and adiabetic transformations. The Carnot engine and cycle. Entropy. Inert matter.
INDEX[377]
THE PHILOSOPHY OF BIOLOGY
CHAPTER I THE CONCEPTUAL WORLD
Let us suppose that we are walking along a street in a busy town; that we are familiar with it, and all the things that are usually to be seen in it, so that our attention is not likely to be arrested by anything unusual; and let us further suppose that we are thinking about something interesting but not intellectually difficult. In these circumstances all the sights of the town, and all the turmoil of the traffic fail to impress us, though we are, in a vague sort of way, conscious of it all. Electric trams approach and recede with a grinding noise; a taxicab passes and we hear the throb of the engine and the hooting of the horn, and smell the burnt oil; a hansom comes down the street and we hear the rhythmic tread of the horse’s feet and the jingle of the bells; we pass a florist’s shop and become aware of the colour of the flowers and of their odour; in a café a band is playing “ragtime.” There are policemen, hawkers, idlers, ladies with gaily coloured dresses and hats, newsboys, a crowd of people of many characteristics. It is all a flux of experience of which we are generally conscious without analysis or attention, and it is a flux which is never for a moment quite the same, for everything in it melts and flows into everything else. The noise of the tram-cars is incessant, but now and then it becomes louder; the music of the orchestra steals imperceptibly on our ears and as imperceptibly fades away; the smell of the flowers lingers after we pass the shop, and we do not notice just when we cease to be conscious of it; the rhythm of the ragtime continues to irritate after we have ceased to hear the band—all the sense-impressions that we receive melt and flow over into each other and constitute our stream of consciousness, and this changes from moment to moment without gap or discontinuity. It is not a condition of “pure sensation,” but it is as nearly such as we can experience in our adult intellectual life.
It is easy to discover that many things must have occurred in the street which did not affect our full consciousness. We may learn afterwards that we have passed several friends without recognising them; we may read in the newspapers about things that happened that we might have seen, but which we did not see; we may think we know the street fairly well, but we find that we have difficulty in recalling the names of three contiguous shops in it; if we happen to see a photograph which was taken at the time we passed through the street we are usually surprised to find that there were many things there that we did not see. Why is it, then, that so much that might have been perceived by us was not really perceived? We cannot doubt that everything that came into the visual fields of our eyes must have affected the terminations of the optic nerves in the retinas; the complex disturbances of the air in the street must have set our tympanic membranes in motion; and all the odoriferous particles inhaled into our nostrils must have stimulated the olfactory mucous membranes. In all these cases the stimulation of the receptor organs must have initiated nervous impulses, and these must have been propagated along the sensory nerves, and must have reached the brain, affecting masses of nerve cells there. Nothing in physiology seems to indicate that we can inhibit or repress the activity of the distance sense-receptors, visual, auditory, and olfactory, with their central connections in the brain; they must have functioned, and must have been physically affected by the events that took place outside ourselves, and yet we were unconscious, in the fullest sense of this term, of all this activity. Why is it, then, that our perception was so much less than the actual physical reception of external stimuli that we must postulate as having occurred? Sherlock Holmes would have said that we really saw and heard all these things although we did not observe them, but the full explanation involves a much more careful consideration of the phenomena of perception than this saying indicates.