Here are thousands around me holding on this or that point opinions differing from mine—wholly in most cases; partially in the rest. Each is as confident as I am of the truth of his convictions. Many of them are possessed of great intelligence; and, rank myself high as I may, I must admit that some are my equals—perhaps my superiors. Yet, while every one of us is sure he is right, unquestionably most of us are wrong. Why should not I be among the mistaken? True, I cannot realize the likelihood that I am so. But this proves nothing; for though the majority of us are necessarily in error, we all labor under the inability to think we are in error. Is it not then foolish thus to trust myself?
When I look back into the past, I find nations, sects, philosophers, cherishing beliefs in science, morals, politics, and religion, which we decisively reject. Yet they held them with a faith quite as strong as ours; nay—stronger, if their intolerance of dissent is any criterion. Of what little worth, therefore, seems this strength of my conviction that I am right? A like warrant has been felt by men all the world through; and, in nine cases out of ten, has proved a delusive warrant. Is it not then absurd in me to put so much faith in my judgments?
-- Thinking as a Science, Henry Hazlitt
> You may not be interested in the dialectic, but the dialectic is interested in you.
It is often mistranslated with "war" in place of "the dialectic" and is often misattributed to Leon Trotsky. 
The dialectic in this case was substantially more politicized than the one Lonsdale discusses. So the mistranslation to "war" is somewhat forgivable. I like this quote because it neatly captures the essence of dialectical thinking. The dialectic is provoking, extremes always are, and once you're engaged it's all-consuming. This isn't a bad thing, Lonsdale is encouraging us to engage with the dialectic, and I believe we should listen to what he has to say. However, the dialectic is a volatile thing, especially the modern dialectic, which might not be too many steps removed from the dialectic of Trotsky's era.
Relevant X-Files scene:
I recently applied dialectical thinking in a discussion about progress in programming. The main question I was trying to answer: "are we make any kind of progress in programming or are we just randomly traversing the space of possible languages and frameworks?" (https://amasad.me/dialectical)
At first it seemed like there is a lot of arbitrary jumping back and forth. One example: in web development we started out by rendering the UI on the server, and then client-side rendering became the norm and now we're back at server rendering with the various "SSR" techniques. This seems like a totally useless hop back and forth. But in reality we might end up in a -- to use Hegel's language -- "synthesis" where we have universal rendering (server + client rendering).
Was that easy to come up with hindsight? Yes.
Was it hard to predict the reiteration of pro and contra arguments? Not really.
Could you use dialectic approach to predict the exact character of follow up arguments? Of course not.
To sum up, none of dialectics observations are important or in any way non-trivial if you put Hegelian grandeur aside. The only attempt to put it for a practical test (Marxist theory of social development) didn't really pan out.
As for it being trivial, to prove otherwise I observe that a lot of things, if not most things, don't follow a dialectical pattern. Most things can worsen, improve, evolve, devolve, spiral, stagnate, or change randomly. Rarely do I find a dialectical pattern in say the weather, the economy, the stock market, my hunger patterns, my mood swings, or my shoes.
Unrelated, I wonder if dielectrics (a material that polarizes in an electric field) maybe were named by scientists aware of philosophy that made a pun.
What he's calling "Nietzschen behavior" is not Niestzchean. But then again, Nietzsche is the most misunderstood philosopher.
Yet, its a common social structure - common enough that we use it without even thinking. And that, I think, is the worst possible outcome - assumption of correctness without correction.
(Oh no, I'm doing it too!)
> But compromise is often even less accurate than the extreme poles of a dialectic.
One problem with dialectic thinking is that, the closer you get to one extreme (pole) being completely "true", the more likely you are to make a synthesis that is less true than the thesis. (This is even more of an issue where someone else is controlling the antithesis - perhaps a debater or a propagandist. In fact, if you're thinking dialectically, and I can supply your antitheses, I may be able to completely control the results.)
On to your comment:
> Yet, its a common social structure - common enough that we use it without even thinking. And that, I think, is the worst possible outcome - assumption of correctness without correction.
In particular, the idea that "dialectically is the correct way to think" is wrong. This is elevating the dialectic from a technique to a philosophy.
Why is that idea wrong? Well, take the statement "dialectically is the correct way to think". Make that your thesis (in the dialectic sense). Then, if the dialectic is correct, there must be the antithesis. I don't know what the antithesis would be, and I don't care; all I need is that there should be one. And then there should be the synthesis. Again I don't care what it is; all I need is that it exists, and it is different from the thesis. So starting with the statement that "dialectically is the correct way to think", and thinking dialectically, we immediately see that the dialectic is inadequate and needs to be replaced (because the synthesis is different from the thesis, and the thesis was that the dialectic is the correct technique).
You mentioned dialectic materialism. That's even worse. Marxist-Leninist philosophy started with materialism (the wrong starting point, in my opinion), proceeded six dialectic steps, arrived at communism, and then stopped. In stopping, they were untrue to their dialectic methodology. If the dialectic is correct, there is an antithesis to communism, and then a synthesis, and after the seventh step, the answer is no longer communism.
And .. 'wrong'?
Perhaps it was the social angle, which makes this relevant?
I'm not really wrong, until my friends and enemies tell me I am wrong .. until them, I'm just .. 'passively disengaged from the dialect' .. or, is it not so?
I totally get you on the philosophy vs. technology approach, though, and I acknowledge (comrade) your identification with my desire to actually bend that particular event horizon.
Second, that "oppositions" in organizations can produce good results
is really a matter of practical prudence following on the recognition
that each of us may have different strengths and weaknesses, that each
of us has a limited perspective or perspectives on reality and that
because of our character flaws, we may take things to extremes. So, to
draw on Lonsdale's example, let's say we have a bureaucrat driven by
an excess fear and desire to eliminate risk and an entrepreneur who is
wreckless, rash and impulsive. When both kinds of person are pitted
against each other at parity, the ensuing conflict can have a
moderating effect on average. It's hardly a perfect situation, of
course. The perfect man would be one in whom these two extremes of
excess caution and wrecklessness are not merely "averaged" into some
arbitrary and bland compromise via some "mechanical or thoughtless
procedure". Rather, "finding the mean in any given situation [...]
requires a full and detailed acquaintance with the circumstances"
. It requires the comprehension of the good and how the
bureaucratic and entrepreneurial can best contribute to it in the
given situation and acting in comformity with this comprehension. This
virtue is called courage.
I fully agree, but I prefer to think of it in terms of Thesis, Antithesis, and Synthesis.
When one has a mental model of how the world works; that's the Thesis. Then one comes across a different model that explains how the world works that contradicts one's Thesis; that's the Antithesis. Over time, one figures out how to reconcile these two contradicting models into a new model; that's the Synthesis.
This model of how thought evolves can be applied to large-scale movements in history. For example, a Thesis of Western capitalist economies in the 19th and early 20th century was that welfare programs were unnecessary in market economies. This led to the emergence of an Antithesis in the form of the socialist movement and eventually communist states, which represented a new form of political and economic organization. Eventually, a new Synthesis emerged: the modern Western welfare state, combining the wealth-generation forces of capitalism with a government-funded safety net that dulls the sharpest edges of the market.
The Thesis-Antithesis-Synthesis model can also be applied to the evolution of scientific thought. For example, a widely held Thesis in Physics prior to Einstein's theoretical breakthroughs was that light must travel through a substance scientists called the "luminiferous aether" in order to satisfy Newton's and Maxwell's equations. However, in experiment after experiment the speed of light somehow always appeared to be constant to all observers, regardless of conditions, which made no sense within the prevailing theoretical framework (Newton's and Maxwell's equations); this was the Antithesis to the prevailing Thesis. Finally, Einsten reconciled the Thesis and the Antithesis into a new Synthesis: the special and then the general Theory of Relativity.
The Thesis-Antithesis-Synthesis model is a great mental model to add to one's arsenal.