In his most famous philosophical work, Dialectics of the Concrete (1963), Kosík presents an original reinterpretation of the ideas of Karl Marx in light of Martin Heidegger's phenomenology.

During the "Prague Spring" of 1968, Kosík became a leading voice for democratic socialism (a distinction he shared with other prominent Marxist humanists like Ivan Sviták and Robert Kalivoda).

[1] French-Brazilian Marxist Michael Löwy and Argentine historian Horacio Tarcus wrote for Le Monde: Karel Kosik is not only one of the most important philosophers of the second half of the twentieth century, but also one of those who best embodied the spirit of resistance of critical thinking.

[3] Organized by Ivan Landa, Jan Mervart, and Joseph Grim Feinberg, it had people from around the world discussing the impact of Kosík's thought on "issues that are still relevant today".

[3][4] Landa and Mervat are working on a "critical edition" of "everything Kosík had ever published or written for print during his lifetime", including books, essays and short notes.