Good inductive reasons

16 February, 2016 at 18:00 | Posted in Theory of Science & Methodology | 2 Comments

Consider a genuine challenge to: ‘April showers have always brought May flowers. So, that April is showery is a good reason for expecting May to be flowery.’ You question whether this is a good reason …


How could I satisfy you as to the goodness of my reasons in the present case? That I have lived through 35 showery Aprils and flowery Mays in several parts of the northern hemisphere would be relevant. So would national and international meteorological records. So would botanical data about the incidence of flowering in differing humidities. So would the general biological theory of plant metabolism. And so would the further fact that no piece of known evidence counts against a showery April being followed by a flowery May; that is, nothing climatologically unusual has occurred which would raise even a mild suspicion as to the expected sequence ‘April’s showery – May flowery’. If I cited all this, then if you are compos mentis, you ought to have been satisfied  as to the goodness of my reasons for expecting May flowers. A questioner who, without being able to cite facts which makes this Spring different from all the others, yet remained unconvinced by such arguments, would either be an idiot or a philosopher, — or both. In either case, he would need therapy.

N. R. Hanson



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  1. Presumably then, someone who expected rapid climate change but could not establish it as a fact to Hanson’s satisfaction would need therapy. This kind of reasoning seems at the heart of much pseudo-science.

    • “The inherent ambiguity of the induction principle and the need for tempering it with assumptions or human judgement opens us to the risk of ‘anything goes’. … Hence it needs to be emphasised that the method of using the best available intuition … has to guard against this risk … While there is no getting away from the use of intuition, we need to harness reason to vet our intuition.”
      Kaushik Basu

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