To connect with these general propositions the different problems which are said to belong to economic science, is the task of the writer of a special treatise on economics. It is your task, esteemed friend, if after having studied these general propositions, they seem to you acceptable. To me it seems that they alone are able to safeguard the independence of economics, not only as distinct from _History_ and _Practice_ but as distinct from _Mechanics_, _Psychology_, _Theory of Knowledge_, and _Ethics_. Naples, 15th May 1900.[97] II _Disagreement (1) about method (2) postulates: (1) Nothing arbitrary in economic method, analogy of classificatory sciences erroneous: (2) Metaphysical postulate that facts of human activity same as physical facts erroneous: Definition of practical activity in so far as admits of definition: Moral and economic activity and approval: Economic and moral remorse: Economic scale of values._ _Esteemed Friend_, Our disagreement concerning the nature of economic data has two chief sources: disagreement on a question of _method_ and disagreement on a question of _postulates_. I acknowledge that one object of my first letter was to obtain from you such explanations as might set clearly in relief our disagreement on the two points indicated.--To reduce controversies to their simplest terms, to expose ultimate oppositions, is, you will agree, an approach to truth. I will explain briefly the two points at issue. In regard to that of method, although I agree with you in upholding the claims of a procedure that is logical, abstract and scientific, as compared with one that is historical (or synthetic, as you say), I cannot in addition allow that the former procedure involves something of the nature of an arbitrary choice, or that it can be worked out equally well in either of two ways. You talk of _cutting away_ a _slice_ from a concrete phenomenon, and examining this by itself; but I inquire how you manage to cut away that slice? for it is no question here of a piece of bread or of cheese into which we can actually put the knife, but of a series of representations which we have in our consciousness, and into which we can insert nothing except the light of our mental analysis. In order to cut off your slice you would thus have to carry out a logical analysis; _i.e._ to do at the outset what you propose to do subsequently. Your _cutting off of the slice_ is indeed an answer to the problem of the _quid_ in which an economic fact consists. You assume the existence of a test to distinguish what you take for the subject of your exposition from what you leave aside. But the test or guiding concept must be supplied by the very nature of the theory, and must be in conformity with it.