1. A textual entailment recognition apparatus for determining whether a first text entails a second text, comprising: a vector generation unit that generates, for each of the first text and the second text, a vector for each predicate-argument structure of the first text and the second text by using a word other than a word indicating a type of argument of a predicate in the predicate-argument structure; a combination identification unit that compares the vector generated for each predicate-argument structure for the first text and the vector generated for each predicate-argument structure for the second text, and identifies combinations of the predicate-argument structures of the first text and the predicate-argument structure of the second text based on a result of the comparison; and an entailment determination unit that obtains a feature amount for each of the identified combinations, and determines whether the first text entails the second text based on the obtained feature amounts.