The Stanford Encyclopaedia of Philosophy defines realism as:
a, b, and c and so on exist, and the fact that they exist and have properties such as F-ness, G-ness, and H-ness is (apart from mundane empirical dependencies of the sort sometimes encountered in everyday life) independent of anyone’s beliefs, linguistic practices, conceptual schemes, and so on.”
By scientific realism I mean here, roughly, realism about entities posited by science, with realism defined as above.
Here I want to give an argument that anti-realism about science cannot capture some of our important practices. The examples I have in mind are from the social sciences and biological, but I suspect examples could be found entangling other sciences. Whether you take this as an argument for realism, or whether you think it is simply so much the worse for our ordinary practices will be a matter of epistemic taste.
Hilary Putnam, in an article I have lost, once suggested that the really interesting failure of scientfic anti-realism is that it can’t explain our practical reliance on sciences. Speaking, from memory, about Popper’s falsificationism he suggested that the falsificationist approach of treating theories as interesting ways of thinking that we haven’t yet shown to be false misses an important dimension- our confidence that we can rely on them to keep being at least approximately true in the future, in domains as diverse as medicine and engineering. How can, for example, falsificationist anti-inductivism explain practices like safety testing where there is a clear implication that we think past results give us reason to be confident about the future?
But let’s suppose that anti-realists could give an account of why we so often comfortably rely on scientific theories to tell us what will happen. There is another problem- one where we rely on science not so much for its ability to predict observations, but for its ability to tell us how things are because we have a direct ethical interest in how things are in themselves- and not just in predictive success.
Consider the psychometrics of happiness, a booming area of philosophical investigation due to the work of authors like Alexandrova. Suppose that we are deciding whether or not to have school start later or earlier, and we have evidence that teens are generally happier when they sleep later and go to bed later. Anyone who thinks that happiness plays an important role in ethical decision making is going to factor this evidence into their decision-making, but it’s not clear that the scientific anti-realist can explain this reliance on social science. Psychometric happiness is, after all, a posited but not directly observable construct. If the relevant science does not give us any reason to actually believe that the children are happier waking up later, then it is hard to see why we should act as if they are happier waking up later- with all the intrinsic value that accrues.
If you want an example from outside the social sciences- consider a neurological investigation that suggests a certain chemical might cause pain and stress to wildlife. This would surely give us some reason to reduce our production of that chemical. Its hard to see how we can understand this reason to reduce as having ethical force if we are scientific anti-realists.