A dialectician is a philosopher who views the world in terms of complementary opposites and the interactions thereof. In popular usage, the central feature of dialectic is the concept of "thesis, antithesis, synthesis" – when an idea or phenomenon (thesis) arises, it carries within itself the seed of its opposite (antithesis), and the interplay of these polarities leads to a synthesis, which is somehow beyond the scope of either polarity alone. In turn, the synthesis is now itself a new thesis, and the entire process can begin again.
Dialecticians sometimes refer to this process as "the negation of the negation," meaning that as soon as the contradiction between thesis and antithesis is resolved by synthesis, the fact that a new thesis has emerged gives rise to a new antithesis and therefore another contradiction. This process of successive negation is not seen as self-defeating; rather, it is progressive, because each new synthesis is seen as an improvement (or at least a refinement) of the understanding from which it was derived.
During the 20th century however some Dialectical Philosophers like Theodor Adorno and Nishida Kitarō developed a notion of Dialectics without a higher unifying synthesis. Adorno referred to this method as Negative Dialectics. The Ideas of Slovenian Philosopher Slavoj Zizek seem to be grounded in a similar spirit, emphasizing the non-unifying and negative aspects of dialectical thought. While Adorno claims that his Negative Dialecitcs are a correction of Hegelian Dialectics, Zizek claims that these negative Dialectics had already been a part of Hegels conception. Arguably this notion of Negative Dialectics originating in Hegels concept of "Negation of Negation" is related to the Buddhist concept of Śūnyatā, which Siddharta Gautama developed in response to the Brahmanist notion of atman - as individual self or soul - which he contrasted with anatman the "not-self".
Historically, dialecticians and dialectical thought have been primarily associated both with the tradition of German Idealism and later with Karl Marx dialectical materialism, which he developed both from and in opposition to the dialectical method of Hegels Absolute idealism. However, individuals widely recognized as dialecticians exist outside of the German Dialectical Tradition. Indeed, dialectic is at least as old as Plato, who argues that it is the process by which one ascends the divided line (cf. "Republic" book VI) to reach the "unhypothetical first principle of everything." Plotinus, too, argued that dialectic was necessary in order to become Intellect, the second hypostasis, in the soul's search for the One. Arguably the Chinese philosophy of Daoism associated with such thinkers as Lao-Tse and Zhuangzi could also be considered a Dialectical philosophy, since it operates with the ancient Chinese philosophical principle of yin and yang. A similar Dialectical Notion can also be found in Hinduism with the concept of the unity of atman and brahman.