This post might just be motivated by my ignorance of the topic, my apologies if this is the case - I just decided to express some vague intuitions that have been in my mind for some time.
The intuition is that a good argument for scientific realism would come from a consideration of the convergence of independent methods and theories towards the same hypothesis. There’s something like this, of course, in Whewell’s ‘consilience of inductions’, and in subsequent work on the robustness of inductive methods. However, the Whewellian line of argument, as far as I understand, is mainly concerned with the reliability of inductive practices, e.g., with how varying experiments corroborates the trustworthiness of their outcomes.
What I have in mind is, instead, some general argument that the convergence of totally independent experimental and/or theoretical procedures towards the same ‘result’ (i.e., the postulation of the same entity, or the same theoretical structure) is best explained by saying that those procedures discover truths (perhaps all this could be put in terms of probabilities, with the probability, say, of the reality of x raising as more and more independent reasons for positing x emerge). As far as I know, something in this sense was said by Salmon (if I remember well, he considered the fact that there are 12 completely different methods of measuring Avogadro’s number as a reason for realism about the latter). But I don’t know of any more systematic treatment.
One could think of it in terms of a ‘detective story’ analogy: in the same way in which independent signs all point to the same (unknown) culprit and - after a certain (clearly vague) threshold is reached - they are sufficient for (quasi-)certainty about the identity of the murder, so independent scientific hypotheses might work together. Of course the objects and the murderer are observables, while the problem with scientific realism concerns the unobservable, but the important point here is that coherence seems to be an indicator of truth, and that the anti-realist arguments in favour of a commitment to mere empirical adequacy seem correspondingly weakened. Here, existing work on coherence and truth (e.g., Bovens and Hartmann), as well as on unification as a theoretical virtue (e.g., Myrvold), becomes relevant but, again, I don’t know of anyone who developed this in the specific domain of scientific realism.
One could say that we simply don’t have evidence of such convergence except in rare cases, such as that considered by Salmon. But this is a historical point- perhaps open for discussion - and doesn’t contradict the conceptual possibility of an argument for realism based on convergence.
Another objection I anticipate is that the convergence towards the same entity is not surprising because we typically tend to use theoretical structure that already exists, maybe in some other field, to explain new problematic evidence. I don’t think this reply has force: consider an alien scientist coming to Earth and illustrating all alien theories to us. It could happen that these theories are very different from ours, and yet (some of them) are based on (some of) the same entities we postulate. Surely, there wouldn’t be a possible pragmatic source for the convergence there, and yet - I think - we would have a strengthened belief in the existence of the entities in question.
Can anyone tell me what is wrong with the idea? Or, if it is not obviously incorrect and was explored before, where I can find something? Even just hearing people’s opinions on this would be nice. (I realise that I have been ambiguous between entity and theory realism here, but I guess it is because the intuition can be developed in slightly different ways).