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" The ordinary logic is also jealous of the explanation of negation as relation, because seeming to take away the principle of contradiction. Plato, as far as we know, is the first philosopher who distinctly enunciated this principle; and though we need not suppose him to have been always consistent with himself, there is no real inconsistency between his explanation of the negative and the principle of contradiction. Neither the Platonic notion of the negative as the principle of difference, nor the Hegelian identity of Being and Not-being, at all touch the principle of contradiction. For what is asserted about Being and Not-Being only relates to our most abstract notions, and in no way interferes with the principle of contradiction employed in the concrete. Because Not-being is identified with Other, or Being with Not-being, this does not make the proposition 'Some have not eaten' any the less a contradiction of 'All have eaten. "
― Plato , Plato: Complete Works