Theoretical philosophy is a broad and complex field that examines the fundamental concepts of existence and knowledge. Synonyms for theoretical philosophy include speculative philosophy, metaphysics, ontology, epistemology, and logic. Speculative philosophy primarily focuses on the nature of reality, while metaphysics deals with the fundamental nature of the universe. Ontology, on the other hand, investigates the nature of being and existence. Epistemology mainly concerns itself with the study of knowledge, belief, and justification. Lastly, logic explores the nature of reasoning and argumentation. While each of these fields is distinct, they all share a common goal of understanding the nature of reality and human knowledge.