Mental Symbols is an essay on mind and meaning, on the biological implementation of mental symbols, on the architecture of mind, and on the correct construal of logical properties and relations of symbols, including implication and inference. The book argues against the main contemporary trends in the cognitive sciences, preferring rather the classical early-modern tradition. The author looks at some logical paradoxes in the light of that tradition, and offers a novel answer to the problem of the biological implementation of the mind in the brain.