The theory that pleasure follows increased vitality, and pain decreased vitality, is supplemented or opposed in modern psychology by the theory that feeling depends on function: that pleasure is the concomitant of medium activities,[182] or of conscious functioning, which is unimpeded and not overstrained[183]--pain accompanying the opposite condition. The objection urged against this view, that it leaves the so-called "passive pleasures" out of account, seems to be made without sufficient consideration of what is meant by attributing passivity to pleasure. All that such an expression can denote, would appear to be that, in the pleasurable experience referred to, no exercise of the muscles is implied, not that such an experience can take place without any conscious activity on the part of the subject. At the same time, the theory that pleasure in all cases depends upon function, must be admitted to be obliged to call in the aid of hypothesis in order to explain all the facts. If the generalisation required by the theory can be made out, it must be by emphasising the fact that feeling is never properly regarded as purely passive, but implies subjective reaction; and by supposing that the variation of feeling between pleasure and pain depends on a difference in the character of this subjective reaction. At the same time, the complete accuracy of this generalisation is not of vital importance here, as it is mainly with the feeling which manifestly results from activity or functioning that we are concerned. [Sidenote: Modification of pleasurable characteristics of objects]