In this part of his life he met his future wife Růžena Grebeníčková (later laureate of Herder Prize), from this marriage came three children (Antonín Kosík, Irena Kosíková and Štěpán Kosík). In 1963, he published his magnum opus, Dialectics of the Concrete, a re-working of Marxian categories in terms of humanist phenomenology, which earned him an international reputation as a leading philosopher of humanist Marxism.
During this period of his life, he met his future wife Růžena Grebeníčková (later Herder Prize winner), with whom he had three children. In 1963, he published his masterpiece, Dialectics of the Concrete, a reinterpretation of Marxist ideas through humanist philosophy, which solidified his position as a leading figure in humanist Marxism.