Notes

0. Introduction
When we disagree, we want our disagreements to be substantive. Substantive
disagreements require agreement on what the disagreement is about, which in turn
requires mutual understanding. Lack of mutual understanding comes from two kinds of
defects: hidden differences in how the parties understand some expression, or hidden
differences in what they take to be the context in which their views are presented. The
former defects are eliminable in principle and manageable in practice; the latter are
something between troublesome and hopeless. So it is important to see how to tell them
apart. One thing seems clear – these defects fall on opposite sides of the divide between
semantics and pragmatics. This is one reason that the divide matters.
Let me elaborate. Suppose you say that the Evening Star is a star and I say it is
not. Ideally, we know well enough what the world would have to be like for our
respective views to be correct: if the shiniest celestial object visible in the sky just after
sunset (discounting the Moon) is a sphere of hot gases radiating energy derived from
thermonuclear reactions you are right; otherwise I am. If we agree about this much, our
debate is certainly substantive. But things could be less then ideal and still good enough
for mutual understanding. Perhaps we don’t both know which one of the shiny objects in
the sky is the Evening Star, or what exactly makes one of those objects a star.