A major competing theory in Ancient Greece for the atomic theory of matter by Leucippus is the essence theory of matter that was devised by Aristotle.
In Aristotle’s essence theory of matter, he speculated that the properties of all matter were given by a fundamental essence.
The most logical solution would be that "he" is this sentence is referring to eh subject of the sentence, the person doing the "refusing", although it's possible that if this were part of a more complex sentence it would be someone else
Malcolm X then served as the public face of the organization for a dozen years, where he advocated for black supremacy, black empowerment, and the separation of black and white Americans, and publicly criticized the mainstream civil rights movement for its emphasis on nonviolence and racial integration.
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