Demystifying Simplicity

When scientists evaluate theories for their plausibility, one consideration that often gets invoked is simplicity. What is puzzling about this is that simplicity is valued, not just for aesthetic reasons or because simpler theories are easier to think about, but because simplicity is taken to be a "sign" of truth. Recent work in statistics has considerably demystified the role of simplicity in a broad class of inference problems. This work allows one to understand the value of simplicity by seeing the connection of simplicity, not with truth, but
with predictive accuracy. An interesting philosophical consequence of this work is that it reopens the debate between instrumentalism and scientific realism.