Dialectics or dialectic is a mode of philosophical argumentation. It can be understood as a way of reasoning that grasps each thought as an incomplete moment in a further unfolding of truth. Contrary to what we're used to in logic, its aim is not to ascribe fixed truth values to propositions, but instead to understand the way in which these propositions are related to our ultimate aim to make sense of the world. As Engels puts it, it "comprehends things and their representations, ideas, in their essential connection, concatenation, motion, origin and ending."
Dialectical method is characterized by the prevalence of contradiction, something which formal logic usually tries to avoid. Contradicting ideas or aspects of things are juxtaposed and allowed to interact with each other, so that we develop a deeper sense of them. This may happen in various ways. Views may get abandoned and replaced with more sophisticated ones, or they may be revealed to actually be compatible with each other. Most interesting, however, is when we discover that the contradiction constitutes a gap inherent to the subject at hand. One that we cannot simply skip over, but that has to be integrated in the way we think about the subject. We may also find that two opposite concepts naturally necessitate each other, which is resolved by a move Hegel called sublation.
Thus dialectics attempts to involve in every thought an apprehension of its own failure. In Hegel's words, dialectics combines "in our process of inquiry the action of the forms of thought with a criticism of them." Since the critique is itself a thought, it cannot stand apart from the object of inquiry. This means the modes of thought "are at once the object of research and the action of that object." This aspect is referred to as immanent critique.
- 1 The Prehistory of Dialectics
- 2 Idealist (or Hegelian) Dialectics
- 3 Materialist (or Marxist) Dialectics
- 4 More Recent Developments
- 5 External Links
- 6 Notes
The Prehistory of Dialectics
The most ancient dialectical method can arguably be found in Plato's dialogues. In these Plato places his teacher Socrates in a debate on some philosophical issue, often as a mouthpiece for Plato's own positions. Characteristic for these dialogues is the use of Socratic irony. Instead of claiming to understand the truth better than his interlocutors, Socrates claims ignorance and asks the other to explain their position. This position is then examined and inevitably loses its credibility, often by leading to some contradiction with the other interlocutor's opinions. The reduction of a premise to a falsehood in order to disprove it is called reductio ad absurdum. The position is then revised, or some other person comes in with an alternative, and Socrates again subjects it to his line of questioning. Paradoxically, Socrates turns out to be the wiser because only he understands how limited his understanding is.
Eventually, however, Socrates will usually start to construct his own (or rather Plato's) opinion on the matter. This process of repeated questioning leading to the refinement of the understanding (or the admission that it is flawed) is referred to as the Socratic method, and is a primitive instance of dialectical reasoning. When it simply has the aim of discovering ignorance, the Socratic method is called elenchus. This process aims at aporia, a state of philosophically useful puzzlement.
Hegel discusses the Socratic method in his lectures on the History of Philosophy. 
Kant understood the term dialectics as
Idealist (or Hegelian) Dialectics
Materialist (or Marxist) Dialectics
The Marxist dialectic, Marx’s Dialectical method or immanent critique, is a sustained inquiry into a subject matter, using its own internal logic, and by locating the internal contradictions, the origins of said internal contradictions become revealed, as well their fate, I.E. how they might be resolved and lead to a transformation of the subject matter.
Any internal contradiction exists as a unity of two opposites, that is, one opposite necessitates the other. Each one of these poles revealed within a contradiction must ungergo self-sublation (sublation is a translation of the technical German word aufheben, which means both to cancel and to preserve something) and pass into its negation, the opposite pole. The opposite pole contains the original pole in its definition, hence preservation and the cycle continues.
The negation of the negation
In order to break this cycle, the poles must be grasped as a whole and to criticise the unity of these two opposites, causing the unity of two opposites in its one-sideness to self-sublate again. This generates a new subject matter that both preserves and cancels out the original matter itself, but in fact is a subject which contains within its definition the original concept and its negation. This method starts with the simpler ideas and eventually leads to more complex ones, which within them, still contain the simpler ideas. The unity discovered from the negation of the negation are not the dialectic themselves, but simply the result of the dialectical method. For examples of these results, see the path of argument used in Capital Vol I.
"Not only has a state of general anarchy set in among the reformers, but everyone will have to admit to himself that he has no exact idea what the future ought to be. On the other hand, it is precisely the advantage of the new trend that we do not dogmatically anticipate the world, but only want to find the new world through criticism of the old one. Hitherto philosophers have had the solution of all riddles lying in their writing-desks, and the stupid, exoteric world had only to open its mouth for the roast pigeons of absolute knowledge to fly into it. Now philosophy has become mundane, and the most striking proof of this is that philosophical consciousness itself has been drawn into the torment of the struggle, not only externally but also internally. But, if constructing the future and settling everything for all times are not our affair, it is all the more clear what we have to accomplish at present: I am referring to ruthless criticism of all that exists, ruthless both in the sense of not being afraid of the results it arrives at and in the sense of being just as little afraid of conflict with the powers that be."