The Hegelian dialectic describes changes in the forms of thought, through their own internal contradictions, into concrete forms that overcome previous oppositions. This dialectic is sometimes presented in a threefold manner, as first stated by Heinrich Moritz Chalybäus, as comprising three dialectical stages of development: a thesis, giving rise to its reaction; an antithesis, which contradicts or negates the thesis; and the tension between the two being resolved by means of a synthesis. However, Hegel opposed these terms. By contrast, the terms abstract, negative, and concrete suggest a flaw or an incompleteness in any initial thesis. For Hegel, the concrete must always pass through the phase of the negative, that is, mediation. This is the essence of what is popularly called Hegelian dialectics.