I shall now very briefly criticize Bacon’s anti-theoretical dogma and his view of science […].
1. The idea that we can purge our minds of prejudices at will and so get rid of all preconceived ideas or theories, prior to, and preparatory to, scientific discovery, is naïve and mistaken. It is mainly through scientific discovery that we learn that certain of our ideas such as those of the flat earth or the moving sun are prejudices. We discover the fact that one of the beliefs we held was a prejudice only after the advance of science has led us to discard it. For there is no criterion by which we could recognize prejudices in anticipation of this advance.
2. The rule ‘Purge yourself of prejudice!’ can therefore have only the dangerous result that, after having made an attempt or two, you may think that you have succeeded – with the result, of course, that you will stick more tenaciously to your prejudices and dogmas, especially to those of which you are unconscious.
3. Moreover, Bacon’s rule was ‘purge your mind of all theories!’ But a mind so purged would not only be a pure mind: it would be an empty mind.
4. We always operate with theories, even though more often than not we are unaware of them. The importance of this fact should never be played down. Rather, We should try, in each case, to formulate explicitly the theories we hold. For this makes it possible to look out for alternative theories, and to discriminate critically between one theory and another.
5. There is no such thing as a ‘pure’ observation, that is to say, an observation without a theoretical component. All observation – and especially all experimental observation – is an interpretation of facts in the light of some theory or other.