[242] Without attempting a systematic classification of kinds of causes, we all know that such is our notion of cause that we can conceive of many causes which bear no assignable quantitative relation with their effects (_i. e._, effects for which they are partly responsible). The pressure of an electric button “caused” the Hell Gate explosion (after conditions—_i. e._, other causes—were prepared) but the amount of pressure put upon this button, or the size of this button, had nothing to do with the quantity of the explosion or the amount of work done in the explosion. We are permitted to speak of the act of pressing the button as a cause, but not as a regulator (except with respect to the _time_ of the explosion, an irrelevant consideration here), for a regulator is a cause the quantity of which determines the quantity of the effect. It should be noted that when the quantity of the cause is compared with the quantity of the effect, to show that the former regulates the latter, the quantity of the cause must be established independently of the quantity of this same effect; otherwise the fallacy of reasoning in a circle is committed. This digression does not lead us so far astray from the theory of value as might be supposed. This precise fallacy has been committed time and again in the reasonings that have been brought to the support of the labor theory of value. For instance when the term “labor” is used to signify disutility or cost (instead of productive power) by the expounders of the “difficulty of attainment” philosophy of value, and it is asserted that the labor cost of a good regulates its value, the objection is soon encountered that skilled labor produces a greater value per day than common. Thereupon it is frequently explained that skilled labor is condensed, or counts as more labor per day than common. As a matter of fact, we all know that in the vast majority of cases, skilled labor, measured independently of the value produced by it, and measured as a quantity of labor in the sense of disutility, is less labor per day than common toil.