 Quine bases his “confirmation holism” upon observations of Pierre Duhem (1914 [1954]), who drew attention to the myriad ways in which theories are supported by evidence, and the fact that an hypothesis is not (dis)confirmed merely by some specific experiment considered in isolation from an immense amount of surrounding theory. Thus, a thermometer will be a good indication of ambient temperature only if it’s made of the right materials, calibrated appropriately, and there aren’t any other forces at work that might disturb the measurement—and, of course, only if the background laws of physics and other beliefs that have informed the design of the measurement are sufficiently correct. A failure of the thermometer to measure the temperature could be due to a failure of any of these other conditions, which is, of course, why experimenters spend so much time and money constructing experiments to “control” for them. Moreover, with a small change in our theories or background beliefs, or just in our understanding of the conditions for measurement, we might change the tests on which we rely, but often without changing the meaning of the sentences whose truth we might be trying to establish (which, as Putnam 1965 [1975] pointed out, is precisely what practicing scientists regularly do).