Bergson's early focus on motion, on change, on evolution, on the flow of time led him to take on those classical philosophers who have seen motion and so change as illusory, most notably Parmenides and Zeno, both Eleatics, whose paradoxes were powerful statements against motion and hence against change. The debate extended into a sense of discontinuous being and the lack of fixity of any sort evident in Heraclitus, a position central to his contretemps with Parmenides. Heraclitus, a process philosopher himself, perhaps the first of that tradition, that is, those who suggest that there are no stable substances per se, emphasized a world of becoming, and such a liminal world in perpetual transition was more consonant with Bergson's sense of durée than the monism of Parmenides and his principal disciple Zeno. For Parmenides, founder of the School of Eleas, our senses deceive us and the real world is apprehensible through logic alone. Everything that is, then, has always been; being is thus unwavering, always complete, and is part of ‘the One’, so that change is mere illusion. Bergson takes on the most pervasive set of proofs for this position, the Eleatic Paradoxes, in almost every one of his works. In Matter and Memory, for instance, he critiques Zeno's ‘proof’ of the impossibility or the illusion of motion by pointing out that Zeno's famous paradoxes ‘consist in making time and movement coincide with the line which underlies them, in attributing to them the same subdivisions as to the line, in short, in treating them like that line’ (Bergson 1991: 191).