Of the three groups, the first, which represents the most extended and radical form of the error, is, as usual, the least harmful, for the reason previously given, that the precise and loyal positions are those that are the most completely surpassed. Several cultivators of economic Science, among the most strict and mathematical, enter upon this desperate struggle against philosophy, which they ridicule as empty chatter and do not merely wish to subdue but altogether to destroy, substituting for it the methods of empirical observation and of mathematical construction, thus favouring a particular empirical and mathematical philosophy of their own, however much they may protest to the contrary. That the pretension is unsustainable, is to be seen, both from the contradictions in which they become entangled and from the very fury that animates them, which is, at bottom, vexation at not being able to free themselves from the contradictions in which they have become involved. For our part, we should like to say to those excellent economists, alike pure and mathematical, did this not appear to be pouring oil upon the flames:--Spare yourselves the trouble of philosophizing. Calculate, and do not think! [Sidenote: _2nd. Universal value attributed to empirical concepts. Example: protection and free trade._] The other group is represented by a particular case of the empiristical error that we have already several times criticized, and many propositions of the kind that one hears in ordinary conversation, against which simple good sense has often rebelled, are to be reduced to it. Thus the empirical consideration of certain human actions as constituting richness and happiness, causes those individuals and peoples who possess property of that sort to be called rich and happy; but to this is opposed, with evident truth, that every one is happy in his own way and that external conditions are not proof of internal satisfaction, which is alone real and effective. The great dispute on free trade is also to be reduced to the same misunderstanding, for when we undertake to demonstrate that wealth is destroyed by protection, the demonstration is efficacious only if the wealth, said to be destroyed, is precisely that of which it was desired to assure the increase by protection; but nothing has been proved if it be a different quality of wealth that it may be desirable to acquire, even with the loss and the destruction of the other. For example, a people may find it advantageous from a political and military point of view to maintain in its territories the cultivation of grain or the construction of ships, even if that were to cost more than to provide itself with grain and ships from abroad; in this case, we should, strictly speaking, talk, not of the destruction of wealth, but rather of the acquisition of wealth (presumed national security), paid for with dear grain and dear naval construction. When the empirical ideas of free trade were raised