In this final column on Engels' dialectics, we discuss another area of dialectics that he developed. We will also mention a significant error, and summarize his influence on the later development of dialectics.

The Dialectics of Knowledge
Engels understood that social practice is the basis of all knowledge, that it is "the alteration of nature by people, not just nature as such, which is the most essential and immediate basis of human thought." Creating theories and testing them in practice is a process that results in a series of partial truths, some of which will be corrected and expanded, and some overturned.
The dialectical development of knowledge includes twists, leaps forward, reverses, and scientific revolutions. Engels said that although some natural or economic laws can be established "in pure form," we usually achieve only partial or approximate truths.
Engels gives the example of Boyle's Law, about the relation between the volume and the pressure of a gas. This law had recently been discovered to be wrong in some cases. Boyle's law only proved to be "approximately true," that is, "true only within definite limits." No one could now prove it to be "absolutely and finally true within those limits."
Failure to understand the dialectical development of knowledge leads to the absurd conclusion that since Boyle's Law can be modified, it is "not a genuine truth, hence not a truth at all." This kind of reasoning is not uncommon in idealist philosophy. Approximate or incomplete truth is not simply wrong, but a stage in the development of knowledge, a stage where our knowledge may guide practice effectively. Further development of that knowledge can lead to more effective practice.

An Important Mistake
Learning from the development of dialectics has to include recognizing some mistakes. Engels got the one we mention here from Hegel, his idealist predecessor. Hegel claimed that motion, even simply moving from one place to another, is a contradiction, an idea that Hegel borrowed from the ancient Greek philosopher Zeno.
It is a central idea of dialectics that contradictions cause motion, but that is quite different from saying that motion actually is a contradiction. Engels made this claim as a major part of his case that contradictions occur everywhere, since matter is in motion everywhere. His argument, dating back to Zeno, is that if something moves, then it must be in some place at each moment but at the same time also not be at that place, which is a contradiction. This is a mistake. Whether you consider the place where an object is located to be a single point or a region of space, motion does not require that a moving thing both be somewhere and also not be there at the same time.
This mistaken idea mattered. It has often been ridiculed by the enemies of dialectics and led to considerable confusion and heated debates as communist philosophy developed in the Soviet Union. The cause of this error was probably Engels relying too much on Hegel.

Influence of Engels' Dialectics
It is hard to exaggerate Engels' influence on the later development of dialectics. His book Anti-Dühring and his pamphlet on Feuerbach were translated into many languages and widely read in the late 19th century. His influence was very important in the struggles against anti-dialectical philosophy that took place in the early years of the Soviet Union. Engels' unfinished book Dialectics of Nature was first published in the USSR in 1925. It was particularly important as an example of integrating the study of dialectics with natural and social science.
This book also became the central target for those who wanted to reject or distort dialectics, claiming that dialectics is simply wrong, or is only about thinking, or only applies to society, not to nature. We will discuss some of these attacks in future columns.

Next column: "Social Democratic" Dialectics