An effective thesis for a comparison essay requires the clear identification of the subjects being compared. The writer must introduce the subjects in a way that helps readers understand their relationship and the rationale behind comparing them. If the essay compares two novels, for example, the thesis should specify the titles of the novels and focus on key comparison points such as themes, character development, and narrative style. Any comparison between dissimilar subjects must be justifiable, with clear reasoning behind why the comparison is made.