Materialism is a fundamental philosophical and/or political worldview which has been in constant opposition with that of Metaphysics. Notable materialists include Heraclitus, Francis Bacon, John Locke, Karl Marx, Friedrich Engels, Nikola Tesla, as well as the tradition of Communism (dialectical materialism).
The Ancient Greek philosopher Heraclitus was a dialectical thinker, who was also materialist in his dialectical wisdom. Examples of this materialism are found in key fragments of his works, which are all but lost to time, such as "No man steps in the same river twice; For it's not the same river and he's not the same man." He was the main contender and confuser of Aristotle and Aristotelian metaphysics.
When most people hear "materialism", they immediately associate it with ideas of greed, desire, or overemphasizing the value of physical things or "wealth" in the human experience. However, critique on the overemphasis of the value of "material possessions", which often comes from a spiritual place, is an implicit critique of "vulgar" materialism (as Marx called it). The vulgarity is essentially in this type of materialism's completely one-sided view that physical material reality is all which exists or all that matters for us to concern ourselves with scientifically. However, this ignores the realm of human subjectivity and therefore human self-critique; in which it is not "material reality" or "material externality" which concerns our scientific thought, but the realm of thought itself (viz. Phenomenology, Psychoanalysis) and its unity and conflict, its relationship with our external/material reality.
In attempting to shield pure (vulgar) materialism and accept it into their thought while also acknowledging the metaphysical realm of thought, the mechanical school was founded by Descartes, who completely estranged his materialist physics from his mathematical metaphysics. For this reason, the materialists of the Cartesian school, or the "anti-metaphysicians", looked to the fresh materialism of John Locke, which had just crossed the river from Britain into France coincidentally. Locke's materialism lent itself to the movement of pragmatism on which the American Revolution for independence was founded, which included Thomas Paine and Jean Jacques Rousseau.
Spinoza collapsed the metaphysical dualism of Descartes (corporeality and the thinking 'I', the Cogito) into One Substance, absolute Being. His idealism conceives this substance in two attributes, thought and extension, and only this absolute unity is reality, it alone is God. Substance is that which exists in itself, conceived by itself, requiring the conception of no other thing as its foundation. All else is finite and therefore accidental. His infinite is not the bare infinite of "and so on to ...." - it is the "absolute infinity, the positive, which has complete and present in itself an absolute multiplicity which has no Beyond .... as a circle is perfect infinity in itself."[1] Hegel only notes that "it might have been better expressed as: It is the negation of negation.”[1] And this is really the problem with Spinoza, his lack of Dialectics. Because negation is only considered one-sidedly in his system there is "an utter blotting out of the principle of subjectivity, individuality, personality, the moment of self-consciousness in Being."[1]
For Spinoza only God exists - against those who would accuse him of atheism (namely, Jacobi), Hegel hurls accusations of cowardice: those who defame him are not "aiming at maintaining God, but at maintaining the finite and the worldly; they do not fancy their own extinction and that of the world." To call Spinoza an atheist is "the direct opposite of the truth; with him there is too much God."[1] However, "in the sense that God is not conceived as spirit, it is atheism." Without Spirit, Spinoza's God lapses into "rigid substantiality."[1] For Hegel however "the Idea essentially includes within itself motion and vitality." With Spinoza there is only a chain of causes, whereas for Hegel the "dialectical process involves cuts, sudden interruptions of the continuous flow, reversals which retroactively restructure the entire field."[2] Essential is that these cuts are not not mere moments within some encompassing process; Zizek gives the example of speech: it is only where the babble cuts off that meaning is retroactively affixed to the entire sentence.
In the same way Marx turned Hegel on his head to discover dialectical materialism, vulgar materialists turn Spinoza on his head. His divine substance is replaced with the substrate of modern science: a physical universe composed of dead matter, atoms and void. But in doing so they share Spinoza's limitations without his brilliance. And ultimately their "substance" is a form. It is idealism. This is why dialectical materialism is the only true materialism - for us matter is not some positive totality with a variety of attributes: society (for instance) is not an organic whole of which classes are parts, it is a radical void, a nothing upon nothing, an antagonism rendered positive only from the determinate perspective of one or another class engaged in struggle.
It wasn't until the dialectical school was revitalized in the West by G.F.W. Hegel around the turn of the 19th century that his "rational kernel" of dialectics, reinverted "as in a camera-obscura" from idealist (metaphysical) back (Heraclitus) into materialist dialectics-- which takes our thoughts and ideas as conditioning external reality as well as external reality conditioning our thoughts and ideas-- that a proper dialectical critique and grounding of materialism in dialectical being was formed. This laid the foundation for the development of Communism as a tradition rooted in and unifying the traditions of Dialectics, science, philosophy, economics, politics, and, of course, materialism. Thus, when Lenin says "You can only become a Communist when you enrich yourself with all the treasures of mankind," he is not only talking about the physical treasures of humanity; paintings, jewelry, ancient artifacts or architecture, machinery; Lenin is including in these treasures different modes of thought, ideas, language, jokes, our spiritual thoughts and feelings-- all of which refer, for Lenin, to the metaphysical treasures of the very experience of living and the social aspect of humanity, which he views as fundamentally materialist.