Definition: In this task, you will be presented with a text and a pronoun. You should write the name that the pronoun refers to. Position of the pronoun in the text is showed within two "_"s.
Input: He distinguished levels of logical reasoning, and introduced the notion of metalogic. Vasiliev spent 1912-13 in Western Europe (mostly Germany) and published his salient works ``Logic and Metalogic'' and ``Imaginary (non-Aristotelian) logic''. Vasiliev constructed non-Aristotelian logic using the concepts, and even the manner of reasoning, common to Aristotelian logic. _He_was aware of the achievement in mathematical logic (and even carefully studied Ernst Schr*der 's works) but did not make an attempt to formalise ``imaginary'' logic. <sep>, Pronoun: He

Vasiliev