07 September 2008

Popper and Peirce on science vs. certainty

Karl Popper, in his Logic of Scientific Discovery (originally published 1934; p. 93-4) used the metaphor of building on a swamp to emphasize that science and absolute certainty don't mix:
The empirical basis of objective science has nothing ‘absolute’ about it. Science does not rest upon solid bedrock. The bold structure of its theories rises, as it were, above a swamp. It is like a building erected on piles. The piles are driven down from above into the swamp, but not down to any natural or ‘given’ base; and if we stop driving the piles deeper, it is not because we have reached firm ground. We simply stop when we are satisfied that the piles are firm enough to carry the structure, at least for the time being.

Popper was at that time unaware that C. S. Peirce, in his Cambridge Lectures of 1898, had used the same metaphor to make the same point, though expressed with a more religious feeling for the scientific enterprise:
The only end of science, as such, is to learn the lesson that the universe has to teach it. In Induction it simply surrenders itself to the force of facts. But it finds, at once—I am partially inverting the historical order, in order to state the process in its logical order—it finds I say that this is not enough. It is driven in desperation to call upon its inward sympathy with nature, its instinct for aid, just as we find Galileo at the dawn of modern science making his appeal to il lume naturale. But in so far as it does this, the solid ground of fact fails it. It feels from that moment that its position is only provisional. It must then find confirmations or else shift its footing. Even if it does find confirmations, they are only partial. It still is not standing upon the bedrock of fact. It is walking upon a bog, and can only say, this ground seems to hold for the present. Here I will stay till it begins to give way. Moreover, in all its progress, science vaguely feels that it is only learning a lesson. The value of Facts to it, lies only in this, that they belong to Nature; and Nature is something great, and beautiful, and sacred, and eternal, and real—the object of its worship and its aspiration.
— (CP 5.589)

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