Challenges to Effective Realism

Abstract

That a theory is merely effective has historically counted against it, especially in pro-realism discourse. For example, many realists take the interpretation of a theory to amount to specifying what the world would be like was the theory true (or characterizing the possible worlds picked out by the theory). But effective theories are not true simpliciter. They describe a limited subset of nature and only approximately so, giving the traditional realist little to work with. The effective realist gives up on the traditional realist project, noting that contemporary physical theories tell us nothing, or very little, about what's fundamental. The traditional realist gives us unreliable results for our ontology at fundamental length scales. Effective realism responds by taking effective theories seriously. I have two primary goals in this paper. First, I consider a few responses to arguments provided by Ruetshce (2017). Ruetsche worries that the theory space over which the effective realist quantifies might fail to be comprehensive. I hope to defend the effective realist through the use of first-order scientific evidence and with a response motivated by Fraser (forthcoming). Second, I develop an objection to effective realism similar in kind to one posed by Ruetshce. Rather than a skepticism in the space on which the renormalization group acts, I entertain a more general skepticism with respect to the construction of effective field theories. I then tease out a response grounded in theory space constraints to justify the effective realist's use of effective field theories to guide ontological commitment.