Abstract

Mediaeval logicians often wrote about changes between contradictory states, for example a switch’s changing from being on to not being on. One of the questions discussed in these writings was whether at the moment the change occurs the changing thing is in the earlier or the later state. The present paper investigates the general setting for that question, and discusses the answer given by Walter Burley, an important early-fourteenth century author whose theory was a standard one. Burley’s theory at first seems arbitrary, and moreover committed to serious theoretical problems. The last part of the paper therefore considers what unspoken factors may have motivated Burley. Certain causal principles are suggested that would remove the apparent arbitrariness and avoid the theoretical problems with his theory, but only at the expense of revising it in a substantive way.