1) Of the Darwinian doctrine I accept the theory of evolution, but Darwin's method of proof (struggle for life, natural selection) I consider only a first, provisional, imperfect expression of a newly discovered fact. Until Darwin's time the very people who now see everywhere only struggle for existence (Vogt, Büchner, Moleschott, etc.) emphasized precisely cooperation in organic nature, the fact that the vegetable kingdom supplies oxygen and nutriment to the animal kingdom and conversely the animal kingdom supplies plants with carbonic acid and manure, which was particularly stressed by Liebig. Both conceptions are justified within certain limits, but the one is as one-sided and narrowminded as the other. The interaction of bodies in nature - inanimate as well as animate - includes both harmony and collision, struggle and cooperation. When therefore a self-styled natural scientist takes the liberty of reducing the whole of historical development with all its wealth and variety to the one-sided and meager phrase "struggle for existence", a phrase which even in the sphere of nature can be accepted only cum grano salis , such a procedure really contains its own condemnation.
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3) I do not deny the advantages of your method of attack, which I would like to call psychological; but I would have chosen another method. Everyone of us is influenced more or less by the intellectual environment in which he mostly moves. For Russia, where you know your public better than I, and for a propaganda journal that appeals to the "restraining effect", [a quote from Lavrov's article] the moral sense, your method is probably the better one. For Germany, where false sentimentality has done and still does so much damage, it would not fit; it would be misunderstood, sentimentality perverted. In our country it is hatred rather than love that is needed - at least in the immediate future - and more than anything else a shedding of the last remnants of German idealism, an establishment of the material facts in their historical rights. I should therefore attack - and perhaps will when the time comes - these bourgeois Darwinists in about the following manner:
The whole Darwinists teaching of the struggle for existence is simply a transference from society to living nature of Hobbes's doctrine of bellum omnium contra omnes [from Hobbes's Elementa philosophica de cive and Leviathan, chapter 13-14] and of the bourgeois-economic doctrine of competition together with Malthus's theory of population. When this conjurer' s trick has been performed (and I questioned its absolute permissibility, as I have indicated in point 1, particularly as far as the Malthusian theory is concerned ), the same theories are transferred back again from organic nature into history and it is now claimed that their validity as eternal laws of human society has been proved. The puerility of this procedure is so obvious that not a word need be said about it.
But if I wanted to go into the matter more thoroughly I should do so by depicting them in the first place as bad economists and only in the second place as bad naturalists and philosophers.
4) The essential difference between human and animal society consists in the fact that animals at most collect while men produce . This sole but cardinal difference alone makes it impossible simply to transfer laws of animal societyies to human societies. It makes it possible, as you properly remark:
"for man to struggle not only for existence but also for pleasures and for the increase of his pleasures ,... To be ready to renounce his lower pleasures for the highest pleasure". [Engles italics — quoted from Lavrov' Sierra article]
Without disputing your further conclusions from this I would, proceeding from my Poppa remises, makes the following inferences. At a certain stage the production of man attains such a high-level that not only necessaries but also luxuries, at first, true enough, only for a minority, are produced. The struggle for existence - if we permit this category for the moment to be valid - is thus transformed into a struggle for pleasures, no longer for mere means of subsistence but for means of development, socially produced means of development, and to this stage the categories derived from the animal kingdom are no longer applicable. But if, as has now happened, production in its capitalist form produces a far greater quantity of means of subsistence and development than capitalist society can consume because it keeps the great mass of real producers artificially away from these means of subsistence and development; if this society is forced by its own law of life constantly to increase this output which is already too big for it and therefore periodically, every 10 years, reaches the point where it destroys not only a mass of products but even productive forces - what sense is their left in all this talk of "struggle for existence"? The struggle for existence can then consist only in this: that the producing class takes over the management of production and distribution from the class that was hitherto entrusted with it but has now become incompetent to handle it, and there you have the socialist revolution.
Apropos. Even the mere contemplation of previous history as a series of class struggles suffices to make clear the utter shallowness of the conception of this history as a feeble variety of the "struggle for existence". I would therefore never do this favor to these false naturalists.
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http://www.marxists.org/archive/marx/letters/engels/75_11_17-ab.htm