The article analyzes Lev Vygotsky’s attempts to utilize Spinoza’s philosophical ideas in solving the methodological crisis of psychology in the 1920s and 1930s. Vygotsky had a manuscript, Uchenie ob emocijakh, where he scrutinized the doctrines of the effects on Descartes and Spinoza. Whilst Descartes’ doctrine built on a dualistic soul versus body premise, Spinoza’s starting point was monistic. Despite his clear sympathies for Spinoza’s solution, which according to him was more compatible with Marxism, too, Vygotsky did not manage to finish (...) his study. One may, indeed, doubt whether Spinoza was able to deliver the decisive key for the solution of the dualism problem, since his philosophy built on metaphysical postulates that were unacceptable to Vygotsky. (shrink)