One Size Fits All

A lot of philosophy - especially bad philosophy - consists in applying a single principle to everything in the universe. For Empedocles it was the war of Love and Strife, for Schopenhaur it was the universal Will, and for Engels it was the dialectic of nature.

In arguing against Dühring's all-embracing system - and indeed against the notion of all-embracing systems - Engels wants to show that his system is superior to that of Dühring...but doesn't want to admit that he's playing the same universe-explaining game as Dühring. So, he fudges the issue.

"...this work cannot in any way aim at presenting another system as an alternative to Herr Dühring's “system”, yet it is to be hoped that the reader will not fail to observe the connection inherent in the various views which I have advanced."
Frederich Engels, Anti-Dühring (1877)

The rest of the book is more honest, piling up examples of how the dialectic accounts for everything which happens or exists, from simple arithmetic to the motion of planets and the nature of revolutionary struggle. Years later, the convert JBS Haldane comes right out and says it.

"...dalectical materialism, the philosophy which, along with Marx, he founded, is not merely a philosophy of history, but a philosophy which illuminates all events whatever, from the falling of a stone to a poet's imaginings."
JBS Haldane, Preface to Dialectics of Nature, by Frederich Engels (1833)