Referring to the concept of “dialectic” has been a promising approach for Activity Theorists to explain development and learning both in societies and in individuals. “Contradictions,” for example, are understood as the “driving force” of development. Often “dialectic” is supposed to work as the theory's most basic foundation. Open questions of this approach, however, are mostly answered simply by hinting at the authorities of Hegel and Marx. This paper's objective is to show that these philosophical roots” of Activity Theory themselves need a critical, philosophical examination before they can be used as a theoretical basis.