I just posted, to a Reddit query entitled "What is Historical and Dialectical Materialism??", at --
-- the following response:
" "Historical Materialism" and "Dialectical Materialism" are not Marx's terms. They are terms associated with Leninist and Stalinist ideology."
"As can be gleaned, starting at least from Marx's Theses on Feuerbach, Marx's theory is no "Materialism" in the sense of an actually Idealist, 'Matterist' ideology, holding that the Abstract Idea of Matter predominates over all other Abstract Ideas, or in the sense of a "Mechanical Materialism"."
"Marx's theory is better described as a 'Psychohistorical Materialism', because Marx always takes the human psyche into account in his theorization of human-social [meta-]evolutions/-revolutions."
"That is why Marx devoted most of his works to the [dialectical, immanent] critique of prevailing ideologies -- why his treatise Capital is subtitled "A Critique of Political Economy"."
"That is why Marx asserted, in his "Economic-Philosophic Manuscripts" of 1844, that the history of human industry, as it objectively exists, is an open book of the human faculties, and a human psychology that can be sensuously apprehended."
"That is why he asserted that '"theory itself becomes a material force"' once it has seized the hearts and minds of the majority class."
"That is also why Marx asserted, in his Grundrisse, "The recognition of the products [by the wage-worker as that worker's] own, and the judgement that [the wage-worker's] separation from the conditions of [the wage-worker's] realization is improper -- forcibly imposed -- is an enormous awareness, itself the product of the mode of production resting on capital, and as much the knell of its doom as, with the slave's awareness that he cannot be the property of another, with his consciousness of himself as a person, the existence of slavery becomes a merely artificial, vegetative existence, and ceases to be able to prevail as the basis of production." [Nicolaus, p. 463, overall italics added]."
"Marx's 'Psychohistorical Materialist' theory is best regarded as arising from a dialectical synthesis of -- via an immanent critique of both -- Mechanical Materialism and/versus Hegelian Dialectical Idealism."