To understand this point of view accurately is not easy, and it is misunderstood by all those who, rather than take it in the concrete, state it absolutely after the manner of an absolute philosophical truth. The theory cannot be maintained in the abstract without destroying it, _i.e._ without turning it into the _theory of the factors_, which is according to my view, the final word in abstract analysis.[6] Some have supposed that historical materialism asserts that history is nothing more than economic history, and all the rest is simply a mask, an appearance without reality. And then they labour to discover the true god of history, whether it be the productive tool or the earth, using arguments which call to mind the proverbial discussion about the egg and the hen. Friedrich Engels was attacked by someone who applied to him to ask how the influence of such and such other historical factors ought to be understood in reference to the economic factor. In the numerous letters which he wrote in reply, and which now, since his death, are coming out in the reviews, he let it be understood that, when together with Marx, upon the prompting of the facts, he conceived this new view of history, he had not meant to state an exact theory. In one of these letters he apologises for whatever exaggeration he and Marx may have put into the controversial statements of their ideas, and begs that attention may be paid to the practical applications made of them rather than to the theoretical expressions employed. It would be a fine thing, he exclaims, if a formula could be given for the interpretation of all the facts of history! By applying this formula, it would be as easy to understand any period of history as to solve a simple equation.[7] Labriola grants that the supposed reduction of history to the economic factor is a ridiculous notion, which may have occurred to one of the too hasty defenders of the theory, or to one of its no less hasty opponents.[8] He acknowledges the complexity of history, how the products of the first degree first establish themselves, and then isolate themselves and become independent; the ideals which harden into traditions, the persistent survivals, the elasticity of the psychical mechanism which makes the individual irreducible to a type of his class or social position, the unconsciousness and ignorance of their own situations often observed in men, the stupidity and unintelligibility of the beliefs and superstitions arising out of unusual accidents and complexities. And since man lives a natural as well as a social existence, he admits the influence of race, of temperament and of the promptings of nature. And, finally, he does not overlook the influence of the individual, _i.e._ of the work of those who are called _great men_, who if they are not the creators, are certainly collaborators of history.