In his Ludwig Feuerbach, Engels declares that the fundamental philosophical trends are materialism and idealism. Materialism regards nature as primary and spirit as secondary; it places being first and thought second. Idealism holds the contrary view. This root distinction between the “two great camps” into which the philosophers of the “various schools” of idealism and materialism are divided Engels takes as the cornerstone, and he directly charges with “confusion” those who use the terms idealism and materialism in any other way.
“The great basic question of all philosophy,” Engels says, “especially of modern philosophy, is that concerning the relation of thinking and being,” of “spirit and nature.” Having divided the philosophers into “two great camps” on this basic question, Engels shows that there is “yet another side” to this basic philosophical question, viz., “in what relation do our thoughts about the world surrounding us stand to this world itself? Is our thinking capable of the cognition of the real world? Are we able in our ideas and notions of the real world to produce a correct reflection of reality?[Fr. Engels, Ludwig Feuerbach, etc., 4th Germ. ed., p. 15. Russian translation, Geneva ed., 1905, pp. 12-13. Mr. V. Chernov translates the word Spiegelbild literally (a mirror reflection), accusing Plekhanov of presenting the theory of Engels “in a very weakened form “ by speaking in Russian simply of a “reflection” instead of a “mirror reflection.” This is mere cavilling. Spiegelbild in German is also used simply in the sense of Abbild]
“The overwhelming majority of philosophers give an affirmative answer to this question,” says Engels, including under this head not only all materialists but also the most consistent idealists, as, for example, the absolute idealist Hegel, who considered the real world to be the realisation of some premundane “absolute idea,” while the human spirit, correctly apprehending the real world, apprehends in it and through it the “absolute idea.”
“In addition [i.e., to the materialists and the consistent idealists] there is yet a set of different philosophers—those who question the possibility of any cognition, or at least of an exhaustive cognition, of the world. To them, among the more modern ones, belong Hume and Kant, and they have played a very important role in philosophical development. . . .’[40] <http://www.marxists.org/archive/lenin/works/1908/mec/02.htm#40n>
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Having pointed out that Hegel had already presented the “decisive” arguments against Hume and Kant, and that the additions made by Feuerbach are more ingenious than profound, Engels continues:
“The most telling refutation of this as of all other philosophical crotchets (Schrullen) is practice, namely, experiment and industry. If we are able to prove the correctness of our conception of a natural process by making it ourselves, bringing it into being out of its conditions and making it serve our own purposes into the bargain, then there is an end to the Kantian incomprehensible [or ungraspable, unfassbaren—this important word is omitted both in Plekhanov’s translation and in Mr. V. Chernov’s translation] ‘thing-in-itself.’ The chemical substances produced in the bodies of plants and animals remained just such ‘things-in-themselves’ until organic chemistry began to produce them one after another, where upon the ‘thing-in-itself’ became a ‘thing for us,’ as, for instance, alizarin, the colouring matter of the madder, which we no longer trouble to grow in the madder roots in the field, but produce much more cheaply and simply from coal tar” (op. cit., p. 16).[42] <http://www.marxists.org/archive/lenin/works/1908/mec/02.htm#42n>
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Engels clearly and explicitly states that he is contesting both Hume and Kant. Yet there is no mention whatever in Hume of “unknowable things-in-themselves.” What then is there in common between these two philosophers? It is that they both in principle fence off “the appearance” from that which appears, the perception from that which is perceived the thing-for-us from the “thing-in-itself.” Furthermore, Hume does not want to hear of the “thing-in-itself,” he regards the very thought of it as philosophically inadmissible, as “metaphysics” (as the Humeans and Kantians call it); whereas Kant grants the existence of the “thing-in-itself,” but declares it to be “unknowable,” fundamentally different from the appearance, belonging to a fundamentally different realm, the realm of the “beyond” (Jenseits), inaccessible to knowledge, but revealed to faith.
What is the kernel of Engels’ objections? Yesterday we did not know that coal tar contained alizarin. Today we learned that it does. The question is, did coal tar contain alizarin yesterday?
Of course it did. To doubt it would be to make a mockery of modern science.
And if that is so, three important epistemological conclusions follow:
1)Things exist independently of our consciousness, independently of our perceptions, outside of us, for it is beyond doubt that alizarin existed in coal tar yesterday and it is equally beyond doubt that yesterday we knew nothing of the existence of this alizarin and received no sensations from it.
2)There is definitely no difference in principle between the phenomenon and the thing-in-itself, and there can be no such difference. The only difference is between what is known and what is not yet known. And philosophical inventions of specific boundaries between the one and the other, inventions to the effect that the thing-in-itself is “beyond” phenomena (Kant), or that we can and must fence ourselves off by some philosophical partition from the problem of a world which in one part or another is still unknown but which exists outside us (Hume)—all this is the sheerest nonsense, Schrulle, crotchet, invention.
3)In the theory of knowledge, as in every other branch of science, we must think dialectically, that is, we must not regard our knowledge as ready-made and unalterable, but must determine how knowledge emerges from ignorance, how incomplete, inexact knowledge becomes more complete and more exact.
Once we accept the point of view that human knowledge develops from ignorance, we shall find millions of examples of it just as simple as the discovery of alizarin in coal tar, millions of observations not only in the history of science and technology but in the everyday life of each and every one of us that illustrate the transformation of “things-in-themselves” into “things-for-us,” the appearance of “phenomena” when our sense-organs experience an impact from external objects, the disappearance of “phenomena” when some obstacle prevents the action upon our sense-organs of an object which we know to exist. The sole and unavoidable deduction to be made from this—a deduction which all of us make in everyday practice and which materialism deliberately places at the foundation of its epistemology—is that outside us, and independently of us, there exist objects, things, bodies and that our perceptions are images of the external world. Mach’s converse theory (that bodies are complexes of sensations) is nothing but pitiful idealist nonsense. And Mr. Chernov, in his “analysis” of Engels, once more revealed his Voroshilov qualities; Engels’ simple example seemed to him “strange and naïve”! He regards only gelehrte fiction as genuine philosophy and is unable to distinguish professorial eclecticism from the consistent materialist theory of knowledge.
V.I.Lenin’s The Theory of Knowledge of Empirio-Criticism and of Dialectical Materialism. II Chapter Two 1. The “Thing-In-Itself,” or V. Chernov Refutes Frederick Engels
http://www.marxists.org/archive/lenin/works/1908/mec/02.htm