Variable Efficacy

Famous quotes containing the words variable and/or efficacy:

“There is not so variable a thing in nature as a lady’s head-dress.”
—Joseph Addison (1672–1719)

“If there is a case for mental events and mental states, it must be that the positing of them, like the positing of molecules, has some indirect systematic efficacy in the development of theory.”
—Willard Van Orman Quine (b. 1908)