Gramsci’s notes on science in his notebooks Quaderni del carcere cast light on the theoretical position of his "philosophy of praxis" towards Italian neo-idealism, on the one hand, and Soviet Marxism on the other hand. Contrary to Italian idealists, Gramsci confided in the results of natural science, despite the fact that he conceived his "absolute" historicism as a dialogue and a correction of Croce and Gentile’s conservative philosophies. Gramsci thought science was rooted in history like all other aspects of culture, ideologies and philosophies. He privileged the history of science as the way to understand science itself. Gramsci strongly criticized the opinions on science expressed by the Soviet Marxist Bukharin in the well known A Popular Textbook of Marxist Sociology and in a speech he delivered at the International Congress of History of Science and Technology which was held in London in 1931. Although Gramsci agreed with him on an "externalist" approach to the history of science, he objected to socio-economical and technical reductionism, as well as to crypto-positivist materialist objectivism. Hence Gramsci’s original attempt to correct Soviet Marxism by the means of historicism, in a manner which is the reverse but complementary of his criticism of Italian neo-idealism.
Keywords: Antonio Gramsci, storia della scienza, Bukharin, storicismo, neoidealismo italiano, marxismo sovietico