Before I now attempt to give the answer I must make one thing clear. What Marx and Engels have left to us as an intellectual inheritance, whether we consider their writings from 1842, or even only those after 1847, seems at first as if it were a confused mass of varied thought-material. Only he who looks closely and who takes the trouble to enter into the spirit of the men can bring the separated lines of thought into order. Such an one finds that some fundamental ideas run through the writings of Marx and Engels during the whole period of their literary activity; also that at different times quite different lines of thought run across and confuse the system which, as a whole, is built up upon these great ideas. Most exponents of the Marxian teaching, especially those representing the middle class, have made the mistake of not separating the essential from the accidental, and have as a result not been able to do justice to the historic significance of these theories. Naturally it is easier to start with the contradictions and inconsistencies of an author, rather than to make tedious tracing of what is of lasting worth; it is easy, but not right, to content oneself with detached and apparent blunders and mistakes in the teaching of an important thinker, in order to reject this teaching _in toto_. Marxism, as no other teaching, offers itself for such treatment; partly because many of his theories awake the passions of the critic and hence must in advance prevent calm judgment, partly because in fact, as already said, it presents a most clumsy confusion of contradictory teachings. This is shown in the fact that even now, after his thoughts have lived through a half-century, we must still exert ourselves to get at the real meaning and the deep importance of his teaching. This is due especially to the "middle-class" critics of Marx; but it is also because of the members of his own party. I recall the fact that the fundamental principle of Marx's economic system--the theory of value--has become an object of fruitful discussion as lately as two years ago. At that time I attempted to bring into use this method which I have just specified as the only true one for such a peculiar formation as the Marxian teaching; I asked how the parts of Marx's theory which stand in such opposition to each other could be reconciled, in order to bring out the sense which so earnest a thinker must surely have laid underneath. At that time the aged Engels could bear witness that I had about "hit the right mark," but that he could not endorse all that I had "introduced" into the Marxian teaching. Other critics thought at the time that nothing more would be heard of Marx's teaching concerning value. Perhaps they are right; but if Marx's _Theory of Value_ is a scientific work, it can be such only in my interpretation.