[CHAPTER IV.]
RELATION OF SENSATIONS TO AN EXTERNAL WORLD.
24. Have our sensations any relation to external objects, or are they merely phenomena of our nature? Can we infer the existence of an external world from the existence of that internal world resulting from the union of the scenes presented by sensations?
This question is theoretical, not practical, and depends solely on the force of reasoning, not on the voice of nature,—a voice stronger than all argument, and irresistible. To whatever result the philosophical examination of the relations of the ideal and the real worlds may lead, we must submit to that necessity of our nature which makes us believe in the existence of such relations. The great majority of mankind never have thought, and probably never will think of making such an examination; and yet they have no shadow of doubt that there exists a real world, distinct from us, but in incessant communication with us. Nature precedes philosophy.
We have no wish to show reason to be unable to vindicate the legitimacy of the inference whereby the real is deduced from the ideal, the existence of the external world from that of the internal; we would only point out a landmark to philosophy, which, if it does not illustrate it, may at least inspire it with sobriety in investigating, and with mistrust in its results. Indeed we cannot but see that that science must be erroneous which is opposed to a necessity, and contradicts an evident fact: it merits not to be called philosophy, if it struggles with a law to which all humanity, not even excepting the philosopher who presumes to protest against it, is inevitably subject. All that can be said against this law, may be as specious as you please, but it will only be a vain cavil, a cavil which, if unanswerable by our weak understanding, nature herself will resist until we shall in another life see the depths of these secrets, and how those links are joined whose points of contact reason cannot detect, although nature feels their irresistible union at every moment of her existence.
25. That sensations are something more than mere phenomena of our soul, that they are effects of a cause distinct from ourselves, is seen by comparing them with each other. We refer some to an external object; others we do not: these two orders of phenomena present very different characters.
I now have within me the representation of the country where I was born and spent my earliest years. I see clearly a vast plain with its fields and prairies, its little hills, now forming only isolated hillocks, now stretching in various directions, sinking to the level of the plain, or gradually rising until incorporated with the mountains, the lofty chain of which surrounds all the plain, and makes it a great amphitheatre, with no outlet except on the south, and here and there a chasm, seemingly torn in the mighty wall reared by nature. All this is very perfectly represented within me, although more than a hundred leagues distant, and this whenever, and as long as I choose. The same spectacle may, perhaps, be offered to me without the concurrence of my will, but I am always free to distract myself from it; I may drop the curtain upon this scene, or raise it anew at my pleasure.
What happens in this case is confirmed by many others; and thus I internally experience a series of phenomena representative of external objects, but am under no necessity to submit to them, for I can abandon or resume them by simple acts of my free will.