3. Classification. Apriorism¶
Core Argument¶
Engels opens his dissection of Dühring’s philosophical system by exposing the idealist core of its foundational method. Dühring proposes that philosophy deals with “principles” — the ultimate, simple constituents of all knowledge and volition. These principles, he claims, are formal tenets derived from thought, not from the external world, and are to be applied to nature and humanity, which must therefore conform to them. Engels immediately inverts this relation: principles are not the starting-point of investigation but its final result; they are abstracted from nature and history, not imposed upon them. To treat principles as prior to the world is to stand Hegel on his feet again — or rather, to stand him back on his head. Engels notes with devastating irony that Dühring’s tripartite division (general world schematism, philosophy of nature, philosophy of mankind) is a direct, unacknowledged reproduction of Hegel’s Encyclopaedia, a borrowing so faithful it would move the Hegelian Michelet to tears.
Engels then drives at the root of the error: the naturalistic acceptance of “consciousness” and “thought” as given, opposed to being and nature. If thought is a product of the human brain, and man a product of nature, then the correspondence between thought and nature is self-evident, not miraculous. Dühring, however, cannot accept this. To avoid any “degradation” of thought by the epithet “human”, he severs it from its only real foundation — man and nature — and tumbles into an ideology that reveals him as a mere epigone of Hegel. Engels warns that no materialist doctrine can be built on such ground, and that Dühring will be forced to smuggle God back into nature under the guise of conscious activity.
The polemic sharpens as Engels turns to Dühring’s treatment of pure mathematics. Dühring claims mathematics deals with the mind’s “free creations and imaginations” and has a validity independent of experience. Engels counters that the concepts of number and figure are borrowed exclusively from the real world: counting arose from ten fingers, geometry from the measurement of land and vessels. The abstract form of mathematical concepts only conceals their empirical origin. Even the apparent deduction of one mathematical magnitude from another proves only rational connection, not a priori origin. Engels points out Dühring’s own self-contradiction: on one page mathematics is the product of pure thought; on a later page, its elements are “completely empirical”. Which are we to believe?
The chapter’s core argument is that Dühring’s apriorism — the attempt to derive the principles of being from thought alone — is a species of idealism that inverts the real relation between thought and the world. Engels insists that the only materialist conception is to treat principles as abstractions from reality, valid only insofar as they conform to nature and history. The broader theoretical context is the struggle against post-Hegelian idealism and the defence of a consistently materialist epistemology. The polemic is directed not only at Dühring but at the entire tradition of system-building philosophy that claims to provide final, exhaustive truths — a claim Engels dismisses as absurd, since any such system would cut short historical development. The contradiction between the drive for exhaustive knowledge and its impossibility is, he argues, the main lever of all intellectual advance.