Dialectics is the art of critically investigating the truth of opinions. Dialectics is the philosophy of metaphysical contradictions and their solutions, especially in the thought of Kant and Hegel; the world process seen as a continuing unification of opposites; the existence or action of opposing forces or tendencies in society etc.
Dialectics is the belief that social organization, culture and intellectual ideas change because of the development of contradictions that create challenges to the existing state of affairs and lead to the emergence of something new from this tension.
Georg Hegel (1770-1831) developed this idea of dialectics in Western philosophy when he claimed that every existing social arrangement or intellectual belief system represents a thesis - a way of doing or thinking about things - that gives rise to a contradictory, or opposing, antithesis.
There is some element of dialectics conception in the writing of Karl Marx (1818-1883) when he claims that contradictions arise in capitalism and the resolution of these contradictions produces a new type of social and economic system.
Dialectical materialism is a concept linked to Marx's ideas, but an expression never actually used in his writing. In this dialectic concept suggests that the process of social change is not attributable to changes in culture or ideas but arises within the material conditions of people's lives, in the way they are organized around economic activity.
In dialectical materialism, the political and historical events are due to the conflict of social forces caused by man's material needs and interpretable as a series of contradictions and their solutions.