This chapter is devoted to the examination of mental entities that lie on the periphery of scientific discourse but play a significant role in the humanities and culture. Particular attention is paid to the notion of the archetype, which continues to be widely used today, despite never having acquired scientific clarity or definition over the course of its existence. It is proposed that the archetype should be interpreted not as an element of the collective unconscious, but as a mental entity formed by history—a multilayered collection of sensory and sensory-verbal concepts associated with entities that are fundamental to human beings (the mother, death, water, war, love, etc.). Using this interpretation, the archetype becomes a set of meanings that reveal, in different ways, the significance of certain entities that are well-known to all people—meanings that have accumulated over the centuries in language, myths, beliefs, folktales, art, and culture. It is a stable semantic structure, represented in objective mental reality and fixed in language, and therefore continues to influence human thinking and behavior. This chapter also discusses the phenomenon of researchers creating new mental entities. Some of these disappear, while others—such as the notion of the “cultural code,” for example—become successfully established in public consciousness. Studying such entities is important as a means of uncovering the deep cognitive and symbolic structures of culture.