for a sentence such as (14a), there is a debate about whether pro moves from spec-vp (where it is introduced) to spec-tp in non-finite clauses. baltin (1995) argues that the tense marker to does not have an epp feature, and that therefore pro does not move to spec-tp; this yields the structure in (14b). in contrast, radford (2004) argues that infintival to does have an epp feature, and that therefore pro must move to spec-tp, as in (14c).