The behavior of two distinct classes of unaccusatives, semantic drift, and idioms provide new evidence that adjectival passives must be derived in the lexicon from the corresponding transitive alternate, whereas verbal passives must be formed post-lexically. Verbal passives are argued to be inserted as two-place predicates, their entire derivation being post-lexical. The set of so-called adjectival passives is split into two distinct subtypes: adjectival decausatives, and adjectival passives. Each of these is argued to be derived in the lexicon, by a distinct operation, involving reduction and saturation of the external role of the input, respectively. The findings support two important currently controversial theoretical assumptions: (a) the lexicon is an active (operational) component, and (b) the external -role is part of the verbal lexical entry, thus accessible to lexical operations. On widely held approaches inserting the external argument via a functional head little-v or discarding the active role of the lexicon, the systematic phenomena presented in the paper would be completely unexpected.