Complex sentence: She was a pioneer in the quantification of modal logic and the theory of direct reference, and conducted seminal research on identity, essentialism, possibilia, belief, moral conflict as well as some critical historical studies.
Split into simpler sentences: She was a pioneering figure in the quantification of modal logic and the theory of direct reference. She wrote seminal papers on identity, essentialism, possibilia, belief, moral conflict as well as some critical historical studies.