Friedrich Engels, answered from the texts and cited to the page.
Dialectical materialism is a coherent extension of the materialist conception of history, and dialectics operates in nature whether we describe it or not.1 The three laws of dialectics — the transformation of quantity into quality, the interpenetration of opposites, the negation of the negation — are features of natural processes that 19th-century science was discovering empirically.2
Marx read Anti-Dühring chapter by chapter, contributed material on political economy, and never disavowed the systematic philosophical exposition.3 Western Marxism's anti-Engels reading is a 20th-century projection that confuses my pedagogical pamphleteering for Marx's silence on these questions.45
An all embracing and determined knowledge of nature and history is in absolute contradiction with the foundations of dialectic thought, but it is not denied, on the contrary, it is strongly affirmed, that the systematic knowledge of the entire external world may from age to age make giant strides.Landmarks of Scientific Socialism - Anti-Duhring
These series, however, are only one particularly obvious example; throughout practically the whole of chemistry, even in the various oxides of nitrogen and oxygen acids of phosphorus or sulphur, one can see how "quantity changes into quality" and how this allegedly confused and foggy Hegelian notion is to be found in so to speak corporeal form in things and processes—and no one but Herr Dühring is confused and…Anti-Dühring, pp. 139–140
This original condition on page 279 is of necessity destroyed by the "robber system"--first negation. But we have now, thanks to the philosophy of reality, arrived at the point of abolishing the "robber system" and substituting for it the economic commune discovered by Herr Duehring--negation of the negation, equality on a higher plane. What is the negation of the negation, therefore?Landmarks of Scientific Socialism - Anti-Duhring
Long live historical treatment in the grand manner! So far we have proceeded from the assumption that Herr Dühring at least showed good faith in his inflexible practice of quoting falsely and that it was due either to his total incapacity to understand things or to a habit of quoting from memory, a habit which seems to be peculiar to historical treatment in the grand manner but which is usually described as…Anti-Dühring, p. 143
It is as Ketteler said about Dollinger: " The man has defended so much nonsense in his life, he really could have accepted infallibility into the bargain! " 53 In fact, mere empiricism is incapable of refuting the spiritualists.Dialectics of Nature, pp. 61–62
The most-attacked Engelsian position. Defended in Anti-Dühring (1877–78), the unfinished Dialectics of Nature (1873–86), and Ludwig Feuerbach (1886). I have not retreated under sustained critique from Korsch, Lukács, the Frankfurt School, Sartre, or the contemporary "two Marxisms" school led by Carver.