By a reasoned change in logic I mean a change in the logic with which you make inferences that is based on your evidence. An argument sourced in recently published material Kripke lectured on in the 1970s, and dubbed the Adoption Problem by Birman (then Padró) in her 2015 dissertation, challenges the possibility of reasoned changes in logic. I explain why evidentialists should be alarmed by this challenge, and then I go on to dispel it. The Adoption Problem rests on (...) a failure to distinguish between logical principles such as Universal Instantiation and Modus Ponens which might or might not govern your inferences with superficially similar laws which must govern your cognitive architecture. (shrink)

In the philosophy of logic, the Adoption Problem is a challenge to the claim that reasoners can, in certain ways, rationally change which logic they use. The (alleged) problem is that if someone does not already infer in accordance with some fundamental logical principles (such as Universal Instantiation or Modus Ponens), then they cannot rationally begin to do so: the “adoption” of these principles is either unnecessary or impossible. In the literature, three issues have emerged as especially contentious: (1) How (...) should we understand the argument for the Adoption Problem? What exactly is the argument’s conclusion, and how is it established, if at all? (2) How could someone who thinks that the rational adoption of logic is possible respond to the Adoption Problem? (3) What are the consequences of the Adoption Problem for related issues in the philosophy of logic? In this paper, we address each question in turn. We suggest that the Adoption Problem is best understood in the form of an inconsistent quartet of theses regarding logical inference. We classify positions on logical adoption in terms of which of these theses is abandoned, and we show that such a taxonomy of positions is useful for delineating the scope and consequences of the Adoption Problem. (shrink)