understanding of why the other would find their viewpoint compelling. This is not the sort of
understanding one finds in a causal explanation, but the ability to see the matter from the other’s
viewpoint. In the case of multiplicity, however, there is no such understanding. Relativism
posits multiplicity, mere pluralism posits disagreement, absolutism posits neither, at least not
under conditions of adequate information, rationality, and cognitive effort.
Even though relativism is an extreme form of pluralism, relativism cannot be equated
with strong pluralism. The distinction between relativism and mere pluralism cuts across the
distinction between strong and weak pluralism. Weak relativism is conceptually possible. That
is to say, we may disagree over values in a relativistic way such that there can be no real
communication about justification, and this disagreement may only pertain to some of our values.
We could still agree on others.
If people with conflicting values can agree on ways of resolving their differences, I leave
it open whether this common ground is rational. Its being common does not rule out its
subjectivity. All normal human adults may be biologically programmed to agree on some crucial
moral assumptions, but this is no guarantee that an Alpha Centaurian, no matter how rational,
would find anything even minimally compelling in these assumptions. The Alpha Centaurian, let
us assume, does not share our biological programming, and hence has a wildly different moral
sense or none at all. Suffice it to say that even if the humanly common ground is subjective, it
may still provide a basis for rational discussion. For example, if every human can agree, upon
proper reflection, that maximizing utility is a basic moral principle and that no other principle
could override it, and even if this agreement is based on nothing rational, i.e. smart space aliens
could deny it, then one is still left with the rationally assessable question of whether or not some
specific act or policy maximizes utility. On the definitions adopted here, this would not be
pluralism. The subjective basis is not enough to make it pluralistic.