Peripherate

To depart from the nucleus (or primary theme) of a discussion, essay or dialogue, and focus on peripheral concepts.

Rater than to nucleate in his thesis (i.e., to focus on the central idea), he began to peripherate.

Peripherate

To move a concept, discussion or item from a nuclear position to one that is Peripheral. To depart from the central focus of a discussion to side issues.

When in a debate, he tends to peripherate, and not stick to the central question.