In theoretical rather than practical terms; theoretically. Sometimes opposed to practically.

on paper: (a) in writing, in print (also upon paper, †in paper (obsolete)); (b) in theory or in principle, rather than in practice or reality.

In name (but not in fact). Also in weakened sense: ostensibly, supposedly; in theory.

in principle: theoretically; in general but not necessarily in individual cases. Frequently opposed to in practice.

In theory, hypothetically. Frequently opposed to actually, practically.