It has often been observed that
if-clauses can behave like arguments as semantic equivalents of
for-to complements. We argue that such usage is accepted in grammar not because
if in question is a complementizer, but because in some environments subordinate clauses, which are PPs, can function virtually like CPs. For a clausal PP to behave like a CP, it must be a recipient of θ-role, and the conjunction must be free of its lexical meaning. These two conditions are fulfilled when
if-clauses (or
when-clauses, for that matter) appear as arguments of predicates assigning the θ-role Object of Emotion. This assumption accounts for triggers, distributions and other properties of this construction.
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