Section 5: Logic & Scientific Method

POPPER ON THE LOGIC OF SCIENTIFIC DISCOVERY

John Worrall,

Department of Philosophy, Logic and Scientific Method,

London School of Economics

London WC2A 2AE, UK

e-mail: [e-mail]

Popper used to joke in his LSE lectures that he was in a somewhat anomalous position, he was
‘Professor of Logic and Scientific Method’, yet he did not believe that there is any such thing as
‘scientific method’ – at least not in the sense of a systematic way of arriving at interesting new
theories. Instead he held the view (one he shared with Reichenbach) that:

The initial stage, the act of conceiving or inventing a theory, seems to me neither to call for

logical analysis nor to be susceptible of it. The question of how a new idea occurs to a man … may
be of great interest to empirical psychology; but it is irrelevant to the logical analysis of scientific
knowledge (L.Sc.D. p.31).

Popper insisted of course that science involves a process of bold conjecture, followed by severe

tests: the testing process is subject to methodological rules, but – by definition – bold conjecturing
is not. Later in his career, he often remarked that the conjecturing process in science is essentially
‘one of error-elimination. It is Darwinian selection, rather than Lamarckian instruction.’

This position is one of the major respects in which his account differs from that of philosophers

of science such as Hanson, Hesse and later Kuhn and Lakatos, all of whom saw theoretical
discovery as at least in part logically analysable. What exactly was at issue in this difference of
opinion has only slowly crystallised. In an earlier paper (1995), I tried to make the issue clear and
to explain in what respects Popper was right and in what respects he was wrong. In this paper –
drawing on a more detailed treatment of one of the historical episodes from physical optics sketched
there – I give a clearer and more adequate account of the issue. In particular I directly address the
questions of (a) why it should matter from the point of view of its empirical support (or
corroboration) how a theory was arrived at and (b) how there can be genuine theoretical discoveries
(involving novel content) if the process of discovery is in a clear sense subject to logical analysis.

Reference:

John Worrall (1995) “’Revolution in Permanence’: Popper on Theory-Change in Science’ in A.
O’Hear (ed) Karl Popper: Philosophy and Problems. CUP