[ar-jan]

For those who won't read the whole thing, here's the relevant part regarding sentences like "I was exhausted":

> The term ‘adjectival passive’ is often applied (perhaps not very felicitously) to active clauses with predicative adjective phrases in which the adjective derives from the past participle of a verb and has a passive-like meaning. There is frequently an ambiguity between be passives and adjectival ones. For example, The door was locked is ambiguous: as a be passive it says that at a particular time someone took the action of locking the door, and as an adjectival passive it says that during some past time period the door was in its locked state. Since the complement in this kind of clause is an adjective phrase, verbs other than be can be used (The door seemed locked, as far as I could tell), and so can adjectives derived with the negative prefix un- (The island was uninhabited by humans).