But I hardly know how to defend myself seriously from such accusations, because it obliges me to repeat what is too obvious, _i.e._, that to make concepts does not mean to _create entities_; that to employ metaphors (and language is all metaphor), does not mean to _believe mythology_; that to construct experiences in thought, and scientific abstractions, does not mean to substitute either one or the other for _concrete reality_; that to make use, when needful, of formal logic, does not mean to ignore _fact_, _growth_, _history_. When Marx expounds historical facts I know no way of approaching him except that of historical criticism, and when he defines concepts and formulates laws, I can only proceed to recognise the content of his concepts, and to test the correctness of his inferences and deductions. Thus I have followed this second method in studying his theory of value. If Labriola knows another and better one, let him state it. But what could this _other_ one possibly be? Real logic? In that case let us boldly re-establish Hegel, it will be the lesser evil, at least we shall understand one another. Or a still worse alternative, what monstrous empirical-dialectic or evolutionist method may it be, which confuses together and abuses two distinct procedures, and lends itself so readily to the lovers of prophecy? Or is it merely a question of new phraseology by which we shall go on humbly working, more or less well, with the old methods, whilst detesting the old words? Or again, is this dislike for formal logic nothing but a convenient pretext for dispensing with any vindication of the concepts which are employed? Marx has stated his concept of _value_; has expounded a process of transformation of _value_ into _price_; has reconstructed the nature of profit as _surplus value_. For me the whole problem of Marxian criticism is confined within these limits:--Is Marx's conception substantially erroneous (entirely, owing to false premisses, and partially, owing to false deductions)? or, is Marx's conception substantially correct, but has it been subsumed under a category to which it does not belong, and has search been made in it for what it cannot supply, whilst what it actually offers has been ignored? Having come to this second conclusion I have asked myself: Under what conditions and assumptions is Marx's theory _thinkable_? And this question I have tried to answer in my essay.