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The justification of induction


To: Scott B.
From: Geoffrey Klempner
Subject: The justification of induction
Date: 15th March 2011 11:28

Dear Scott,

Thank you for your email of 3 March, with your essay for the University of London BA Methodology module, in response to the question, 'Is it possible to justify the claim that inductive reasoning is a reliable method of acquiring true beliefs? If it is explain how. If it is not, explain the consequences for our inductive practices.'

This is a good essay. My impression is that you have relied quite heavily on the text book for your answer. Which is OK, I'm not criticizing you for that. The basis for this hypothesis would be difficult to formulate in the way that you have formulated the inductive inference regarding emus, but it is based on my subjective impression, no more than that, that some of the language that you use is textbook-ese rather than essay-ese. I'm hearing your voice, as it were, but not all of the time.

I am taking into account the fact that the work you have sent me has shown a steady improvement, and that in the past you have shown yourself to be articulate, especially when it comes to expressing or explaining a philosophical problem in a way which the reader will find gripping, an ability which not all of my UoL students possess to the same degree.

Because this is in many ways a text-book answer, it is difficult for me to find any objections to what you say. In an examination, you would get a good mark for this. So what I am going to do instead is try to look at things a bit from the side, in the hope that this might stimulate you to ask questions that you might not have considered.

There are really two questions that need to be unpacked. One concerns the challenge to inductive reasoning, as such, posed by Hume. Hume has an ulterior purpose: he is seeking to demolish the traditional claims of philosophy in order to make room for his new science of human nature. I don't think it is too far fetched to see Hume as aspiring to be the Newton of the human mind. The object of the exercise is to undermine the whole idea of 'justification' and 'reason' as it had hitherto been understood.

Today, a Humean naturalism is assumed as the starting point of much of philosophy of science and methodology. Yet we still speak of 'justification' and 'reasons', 'good grounds' for beliefs, and so on. That is because science has a vested interest in making choices between theories, deciding when the evidence is sufficiently strong to support a given theory, or when two or more theories are equally well supported. How are these choices to be made?

One can speak of 'external' and 'internal', not in the sense which you use, i.e. externalist and internalist theories of justification, but rather in Carnap's sense of a distinction between questions about a given framework -- in this case, the framework of hypothesis formation, inductive reasoning, etc. as employed in science -- and questions within the framework, such as whether a particular theory is sufficiently well supported, where the validity of the framework does not come into question. (Look up 'Carnap on internal and external questions' in Google.)

I can well understand someone like Stephen Hawking complaining that contemporary philosophy of science fails to address the interests and concerns of working scientists. The idea that one can argue over whether induction, as such, is 'justified' or not seems absurd, especially when one considers the real challenges which scientists face, not just concerning how one decides between theories, but more often how one finds a single theory that 'works'. I think he has probably over-stated the case (you might say, a typical example of an expert in one field making pronouncements in a field where one lacks expertise) but even so there is a worry that much philosophy of science and methodology is now seen as irrelevant to science.

I suspect that there is a false assumption lurking here, which it is the duty of philosophy to bring to light, which is in a way the legacy of the 'school philosophy' that Hume sought to demolish. Scientists believe, they have to believe, that what they do expands human knowledge. And yet, in so many cases, the decisions we make, say, concerning 'how well' evidence supports a given theory cannot be further justified or supported by reasoning. Science is, at bottom, 'unscientific'. The argument for the alleged circularity in attempts to justify inductive reasoning 'as such', can equally be applied to 'internal' questions (in Carnap's sense) about the decisions working scientists make, the debates in the pages of Physics journals for example. There is no 'method' or higher court of appeal, only the judgements of working scientists, the only ultimate test for which is agreement with the judgements of other working scientists.

This is the 'problem of induction' with a vengeance. Because this isn't about whether we should practice induction at all (no-one is seriously saying we shouldn't not even Popper -- who is still interested in 'corroboration') but about what counts as good science, if indeed there is anything that philosophy can contribute to this debate.

All the best,