Proportionality

Stephen Yablo (Massachusetts Institute of Technology)

Abstract

Proportionality does a lot of work in philosophy. Causes should be proportional to their effects. Reasons should be proportional to what they rationalize. An  argument's premises should ideally be proportional (wholly relevant) to its conclusion. Truthmakers are ideally 'discerning' (Armstrong).

But what is it for X to be proportional to Y? The usual story is that to be proportional is to be minimally sufficient; nothing less would have done. This can't be right. Minimally sufficient conditions often do not exist, and we do not always insist on them when they do exist. What then is proportionality?