Something you have to understand about Hegelian dialectics is that there is two forms. One is what is in the Phenomenology of the Sprit/Ghost/Mind and the other is the formalized structure in the Logic. So what is happening in the phenomenology of mind is not exactly formal, not exactly perfectly dialectical in terms of format. So what is in the Phenomenology of Geist is so much more interesting than the later formalize of ‘Dialectics’ that we get in the Logic. It is clear that History does not follow any formal rule. So the idea that History is dialectical in the formal sense clearly wrong even if we can get approximations when we project it onto history. But the idea of History being dialectical in the looser sense is still of some interest. This is because the idea is that at a given time in intellectual history, all the possible permutations appear and ultimately cancel each other out giving rise to a deeper view, and then the same thing happens with the deeper view. The perfect example of that is the pre-Kantians and their dogmatic philosophies prior to Kant’s Copernican turn. Kant’s transformation of Philosophy has determined the direction of philosophy ever since. And if you look at the commentaries on Kant and all the post-Kantian philosophies then you can see that every possible interpretation of Kant has been tried out, without anyone escaping the limits that he set on reason that ground Science even to this day. He only wanted to ground Newtonian science, but ended up defining Science itself from his time till now. But there have been within this space he opened up some crucial philosophical developments within that conceptual space as philosophers grappled with the fundamental philosophical problematic he set up. So if we look at the different ideas and their relation to each other what we notice is that over time as the problematic develops all the permutations tend to cancel each other out, and eventually someone will come up with a fundamental transformation that will reset the playing field, and start the dialectical process all over again. In the formalized view given by Hegel later the driver of the process became negation, but the real driver is the fundamental human nature that produces variety, and the permutational exploration of the space of possible Science grounding philosophies. And it is possible to see when we study the space within the problematic that the various views are arrayed antithetically to each other in such a way that they ten to balance each other out. And this is natural phenomena according to Hegel with his idea of Absolute Reason. Absolute reason actually is just science applied to History and says that everything in history because it is in the universe governed by physical laws has a reason. So if you look at any phenomena closely enough you will see absolute reason playing itself out in all phenomena. Historical phenomena is just a horizon that is infinite and so it is turtles all the way down, i.e. there is reason all the way down, natural laws apply to everything and so whatever you look at no matter how detailed and minute has a reason. And part of that reason is the natural variation of our interpretations of history and events on which there are multiple perspectives that tend to cancel themselves out. When we realize this cancellation that comes from the human intellect producing antimonies we can see that it is superseded by a different view that is deeper and then the antinomies play themselves out at the next deeper level of understanding or comprehension of the phenomena.
Hegel justifies his view by saying we live in a law governed universe and that the natural laws apply to everything and thus all things have sufficient reason for their existence from the laws of nature. But just because we can say that in general, and we have even more reason to say that now, does not mean we know the reason, that is a speculative activity to produce interpretations that contain those reasons. The dialectics have more to do with our ways of seeing the reasons and our interpretation than the actual mechanism of history itself. For instance if a process is random the that is the reason it is the way it is. But there are different interpretations of what randomness is and those tend to cancel each other out. What drives history is natural laws operating and emergent levels that articulate phenomena. When we look at that phenomena we know it is driven somehow by natural law at given emergent levels. But our different views of the phenomena tend to cancel each other out unless there is a symmetry breaking in which some new view supersedes all the others. Then we get the same variety production of view until a new symmetry breaking occurs. The succession of views based on the cancellation of interpretations and permutations of ideas is the expression of the dialectical development in the history of ideas. The phenomena does not necessarily change but our interpretations of it can change radically. Thinking this happens though negation only is just a reductionist and reified view of a interesting and dynamic process by which our understanding of the natural world and ourselves improves over time by a lot of hard work by a lot of people toiling at the business of science over the centuries. The justification is the lawfulness of nature. The workings of absolute reason as a reflexive self-consciousness about history can be seen in every field in which myriad theories are produced until one turns out to be either more interesting or better at explaining facts than others, and then we readjust and begin building from there. This process is absolute reason working itself out on history of consciousness and applied to a world in which everything is determined in some way by physical laws that hem in our expression of inner freedom.
[This answer needs improvement 2012.08.15 kdp]