Scientific Realism and Blocking Strategies

This paper concerns the epistemological dimension of the scientific realism debate. A short explication about what that amounts to is due. One needs to differentiate between characterising being an epistemological scientific realist and epistemological scientific realism. I understand being an epistemological scientific realist as being committed to believing that unobservable1 entities and/or structures, as put forward by a proper subset of our scientific theories, exist. Epistemological scientific realism is the position that

those beliefs have some kind of rational standing (e.g. justification, warrant, reasonableness)2 based on scientific investigation and

contending further that such rational standing is strong enough to epistemically obligate one to believe in said entities and/or structures.3

Chakravarty classifies the scientific realist similarly when saying ‘it is the naked fact that she believes that makes her a scientific realist’ (Chakravartty and van Fraassen 2018, 23). This is a classification with quite a low demand. Suppose I tell you to believe in electrons, but knowingly my belief is a pure leap of faith, then I am a minimal realist in this sense, but my realism does not have any strong epistemic commitment. In fact, I openly do not have any epistemological standing towards my belief.4 As such, the important epistemological questions are (i) and (ii)—the ones about norms of belief.

My explication of scientific realism in terms of some form of justification is common5 but it is even more common to explicate the rational standing in terms of knowledge (e.g. Boyd 1983; Hacking 1983; Ladyman 1998; Chakravartty 2017) even though I think this is quite problematic because it packs the goal (true believing) and the methods (justified believing) into one complex concept.6 Still, for the purpose of this article, I will not have any quarrels with ‘knowledge’ either.

Condition (ii) is to exclude such constructive empiricists from the realist camp who believe in unobservables but also believe that there is no rational obligation for this belief. One objection to condition (ii) might be that it also excludes some voluntarist realists, such as Chakravartty, so maybe (ii) is too strong. I will talk about voluntarism later. For now, this should make my target sufficiently clear.

Today, many philosophers of science think that the realism debate is at a stalemate or even a dead end (cf. Blackburn 2002; Magnus and Callender 2004; Monton 2007, 3) and this sentiment is nothing new (cf. Fine 1986, 136–150; Nagel 1961, 145; Wylie 1986, 287). Why is this the case? We should distinguish three dimensions where the disagreement can be stuck:

The Synchronic Evidence Dimension: empirical evidence in support for a given scientific theory

The Diachronic Evidence Dimension:

Historical Evidence: present empirical evidence from episodes in the history of science about theory change

Prospective Evidence: yet unavailable evidence from historical scientific episodes and future scientific developments about theory change

The Value Dimension: considerations about attitudes, commitments, values, epistemic standards, and epistemic goals

Note first that the application of synchronic evidence to the realism debate is very limited. It is the main concern for working scientists, but the philosophical debate goes a different route with some exceptions.7 This is simply the case because in the current discussion all rival accounts are constructed for synchronic empirical adequacy.

Next, consider diachronic evidence. Historical evidence is often associated with the Pessimistic Induction [PI].8 The interesting feature of it is that, contrary to the synchronic evidence dimension, it cuts through a wide variety of rival accounts. Here, at least to some extent, the disagreement is about what the evidence shows. This is a healthy aspect of the debate because it allows evidence-based comparisons.9 Still, various rival accounts claim the historical track record being on their side.10 In this paper, I argue that one can distinguish positions in the realism debate that are open to refutation by historical evidence or by the future progress of science, and those that are not open to such refutation, and we should reject all those positions that are not open to such refutation.

Before I get to this main point, I need to say a few words about the value dimension.