Today Vygotsky's theory is usually associated with a short list of ideas: which includes social formation of the human mind, zone of proximal development, semiotic mediation, and egocentric and inner speech. Vygotsky's theory contains these and many other ideas indeed. In today's interpretation, however, all the mentioned ideas are transformed into slogans with trivial content or even into a set of statements that contradict many facts known about the functioning of the human body and human mind. Vygotsky relied explicitly on epistemology I have called structural-systemic. According to this epistemology, in order to understand human mind scientifically, its structure needs to be discovered. The studies need to reveal the elements from which the mind is composed, the specific relationships between the elements, and qualities of the whole that emerges in the synthesis of the elements. Only developmental studies can answer these questions because the properties of the elements change when integrated into a whole. His epistemology can be opposed to that dominant today, which aims only to the discovery of relationships between events, to the discovery of ''causes'' that make the ''effect'' to happen. In Vygotskian structural-systemic perspective, the same theoretical ideas acquire meanings very different from modern interpretations.