Recent research has highlighted a remarkable variability in subject island effects. Focusing on intransitive verbs and adjectives, we argue that islandhood is determined at the syntax-semantics interface: subjects qualify as islands when they are interpreted outside the predicative nucleus of the clause, in a categorical LF structure ( Ladusaw 1994 ); they are transparent for extraction when they undergo total reconstruction into the predicative nucleus, giving rise to a thetic structure. The thetic/categorical interpretation depends on various factors (most notably the stage-level versus individual-level nature of the predicate), whose interaction accounts for the observed variability of island effects, as shown by our experimental evidence. The relevance of subject reconstruction need not be stipulated; rather, it follows from a top-down-oriented computation, in which movement dependencies are implemented by a storage-and-retrieval mechanism.