The second elementary form of cost is that emphasized chiefly by the Austrian writers. In the making or acquisition of economic products, certain scarce agents are either destroyed, or else for the time being employed in a way that excludes their employment in the production of other goods. We may say that the production of any given good involves the destruction of certain productive agents, or, permitting a convenient liberty of expression, of the uses of agents from which other goods might have been produced. Thus with the emergence of one good the possibility of some other good is excluded. Professors von Wieser and Böhm-Bawerk, who have written the best explanations of the relation of this form of cost to value, have suggested no distinctive name for it. The reason appears to be that they consider this as the only form of cost which requires especial explanation, since, as they hold, it is the only kind of cost which can be correlated with value. In an article in the _Quarterly Journal of Economics_,[204] Professor D. S. Green has suggested the term “opportunity cost” for the Austrian conception. Professor H. J. Davenport, having in mind the same conception, refers to it as “sacrifice cost.”[205] Professor Heinrich Dietzel speaks of the same cost as “_Nutzeneinbusse_.”[206] This concept has also in various places been designated “social cost.” Though this cost is social in a certain comparatively irrelevant sense in which the other kind of cost is not social, the term “social cost” is not a good one because it lacks distinctiveness. There is nothing intrinsically social about potentiality cost, nor would the other elementary form of cost, that is, pain cost, be best designated “individual cost.” Both forms would appear in an isolated individual economy, for instance in our fictitious but highly useful Crusoe economy. “Sacrifice cost” is ambiguous, because the word “sacrifice” is used as often as not, though perhaps improperly, to signify the discomfort or pain endured in production. A term is needed to distinguish a form of cost from pain cost. “Potentiality” cost appeals to the writer as being a term somewhat better than “opportunity” cost. When certain common production goods, capable of being turned to the making of more than one kind of thing, are used up to make a given thing, their potentiality to make an alternative thing is destroyed. The potentiality cost of a commodity is measured by the highest other value that might have been obtained if this commodity had not been produced from the productive agents entering into it.