Examples from Scientific Practice

The notion that pursuit is normatively unconstrained is at odds with scientific practice. First, scientists do in fact sometimes defend the pursuit of theories, something which would be superfluous if there were no normative standards for pursuit. For example, Achinstein (1993) discusses Niels Bohr’s early quantum theory, published in three papers from July to November 1913. In these papers, Bohr notices that Rutherford’s atomic model faced certain theoretical problems. To resolve these, Bohr proposes several at the time radical proposals for revising the model. These include the assumptions that electrons can only move in certain stable orbits and that radiation is only released when an electron “jumps” between these orbits, violating classical electrodynamics. Finally, Bohr derives an expression from the revised model for the wavelength of light emitted from a hydrogen atom similar in form to the experimentally determined Balmer formula (Achinstein 1993: 95-98).

As Achinstein points out, Bohr does not claim his theory to be correct or even probable. Furthermore, in letters to a colleague, Bohr acknowledges its speculative character: “For the present I have stopped speculating on atoms. I feel it is necessary to wait for experimental results” (Bohr to Mosely, 21 November 1913, quoted from Achistein 1993: 98). While the positive results gave him “hope to obtain knowledge of the structure of the systems of electrons surrounding the nuclei in atoms and molecules”, he also emphasised that he did not think this was achieved by “the result which I mean I can obtain by help of my poor means, but only of the point of view … which I have been led to by considerations such as those above” (Bohr to Hevesy, 7 February 1913, Achinstein ibid.). However, Bohr did regard his articles as a defence of the model: he was trying to convince his colleagues that it was worth pursuing, by testing the model’s

predictions experimentally and trying to further develop its “point of view”, i.e. its general idea. Since Bohr gives arguments in favour of the model, he recognises that his peers, at least implicitly, endorse some constraints on what it is worth pursuing.

Secondly, scientists in a given field only pursue, and indeed could only pursue, a limited number of theories. They need to prioritise their time, efforts and resources and consequently regard some proposals as clearly a waste of these. For example, McKaughan (2007: 20-24, 291) points out that the particle physicist Steven Weinberg in his Dreams

of a Final Theory admits that the theories which he proposes and works on are “of limited

validity, tentative and incomplete” (Weinberg 1992: 13). Weinberg nonetheless insists that these theories are “worth taking seriously” (Weinberg 1992: 103); despite their likely flaws, he thinks that it is reasonable for him and his colleagues to spend their time working on these theories. He also makes clear that not every tentative theory has this status:

I receive in the mail every week about fifty preprints of articles on elementary particle physics and astrophysics, along with a few articles and letters on all sorts of would-be science. Even if I dropped everything else in my life, I could not begin to give all of these ideas a fair hearing. So what am I to do? Not only scientists but everyone else faces a similar problem. For all of us, there is simply no alternative to making judgements as well as we can that some of these ideas (perhaps most of them) are not worth pursuing. (Weinberg 1992: 50)

As Weinberg points out, this is a general problem: due to the limited time and resources, scientists are forced to make judgements about which theories should be prioritised. We saw in the previous chapter that Peirce also took abduction to be based on economic considerations. In fact, Peirce at one point gives an argument very similar to Weinberg’s. Having claimed that abduction shows that a theory should be given “a high place in the

list of theories of those phenomena which call for further examination”, he pre-empts an objection:

If this is all his conclusion amounts to, it may be asked: What need of reasoning was there? Is he not free to examine what theories he likes? The answer is that it is a question of economy. If he examines all the foolish theories he might imagine, he never will (short of a miracle) light upon the true one. (CP 2.776)

As the Bohr case illustrates, scientists do not make these judgements blindly: they consider some theories more reasonable to pursue than others and give arguments for why their preferred theories should be pursued.

The fact that scientists do in fact recognise the need to make such judgements, and present arguments for doing so, indicates that this is an aspect of scientific reasoning which is subject to normative constraints which philosophers can attempt to spell out. As with any aspect of scientific practice, it can of course turn out that no plausible normative account can be given. Weinberg’s judgements about pursuit worthiness may simply boil down to idiosyncratic preference. However, Weinberg (and Peirce) do highlight a plausible basis for making normative judgements about pursuit: there is only a limited amount of time and resources available for research, so scientists should focus on those theories that promise the most epistemic output for the time and resources invested in them.33 _{I conclude that it is reasonable to try to formulate such a normative account of}

pursuit unless there are principled reasons why it could not succeed. I will now consider some candidate reasons for this.

33 _{As I argue below (Sections 2.3.2 and 2.6), even if scientists had infinite resources, there are further}

normative constraints on pursuit, namely whether anything interesting could be reliably learned from pursuing the theory.