The science of Exchange, or, as I hear it has been proposed to call it, of "Catallactics," considered as one of gain, is, therefore, simply nugatory; but considered as one of acquisition, it is a very curious science, differing in its data and basis from every other science known. Thus:--If I can exchange a needle with a savage for a diamond, my power of doing so depends either on the savage's ignorance of social arrangements in Europe, or on his want of power to take advantage of them, by selling the diamond to any one else for more needles. If, farther, I make the bargain as completely advantageous to myself as possible, by giving to the savage a needle with no eye in it (reaching, thus, a sufficiently satisfactory type of the perfect operation of catallactic science), the advantage to me in the entire transaction depends wholly upon the ignorance, powerlessness, or heedlessness of the person dealt with. Do away with these, and catallactic advantage becomes impossible. So far, therefore as the science of exchange relates to the advantage of one of the exchanging persons only, it is founded on the ignorance or incapacity of the opposite person. Where these vanish, it also vanishes. It is therefore a science founded on nescience, and an art founded on artlessness. But all other sciences and arts, except this, have for their object the doing away with their opposite nescience and artlessness. _This_ science, alone of sciences, must, by all available means, promulgate and prolong its opposite nescience; otherwise the science itself is impossible. It is, therefore, peculiarly and alone, the science of darkness; probably a bastard science--not by any means a _divina scientia_, but one begotten of another father, that father who, advising his children to turn stones into bread, is himself employed in turning bread into stones, and who, if you ask a fish of him (fish not being producible on his estate), can but give you a serpent.