8. We may now essay a partial summary of the results which have been reached up to this point. The end of the theory of value is primarily to explain exchange value. The only workable definition of this term is purchasing power. The purchasing power of a commodity is measured objectively in terms of the physical units of some other particular good, except when we are speaking of the concept of an article’s _general_ purchasing power. This, its purchasing power over all other commodities,[264] is measured as some kind of mean or average of all its particular purchasing powers. What mean, it is no part of our task to enquire. All goods which possess exchange value also possess that other kind of worth which we termed “esteem value.” Every commodity derives its exchange value solely from its esteem value, or, speaking with precision, from its esteem values. For a commodity has a separate esteem value to each individual person who can utilize it. If society were as one man,[265] the exchange values of goods would be but the exponents of their relative esteem values. In other words, if a physical unit of one commodity exchanged for two units of another, the reason would be merely because the first possessed twice as much esteem value to all society as a unit of the second. But the esteem value of an article is a much more definite thing than a social estimate, _i. e._, an “average” (or typical) estimate of worth. The esteem value of a good to a person is the measure of the amount of that person’s satisfaction conditioned upon the enjoyment of the good. Goods existing in superfluous abundance give satisfaction but do not condition it, and hence lack esteem value. Taking for granted the amount of an individual’s income, the esteem value which a good has for him determines his price equivalent for that good.[266] The market price, or exchange value, of a good is a _resultant_ from (never in any sense an average of) the individual price equivalents placed upon it by the body of individual consumers.