A DD debate is unfolding between him and her.

He strongly advocated the hokushin theory.

He strongly advocated the theory of southward advancement.

He believes in teleology, thinking that there is a meaning in every event.

He is writing a thesis on the yellow peril.

His idea is pure armchair theory and cannot be applied to real-world problems.

He is an expert in syntax and has written many papers.

He is an expert in semiotics, and his theories are very profound.

He has a deep interest in number theory.

Number theory is a branch of mathematics that primarily studies the properties of integers.