Lenin's theory of knowledge was part of orthodox Marxism-Leninism in Poland. But beside it another trend of thought had appeared among the younger generation of Marxist-Leninists, who were becoming increasingly dissatisfied with what the official doctrine had to say on the problems of knowledge. The leading spirits of this trend were Helena Eilstein, Zdzisław Kochański, and, above all, Leszek Kołakowski. Kołakowski's ideas have a considerable affinity with and are largely derived from the views of the young Marx, to be found in the unfinished manuscript Nationalökonomie und Philosophie. In Kołakowski's interpretation, the young Marx held a conception of knowledge radically different from the positivistic epistemology to which he and Engels later subscribed, and also from that prevalent in contemporary Marxism-Leninism, based mainly on Lenin's Materialism and Empirio-Criticism.