Philosophy of Physics: A Very Short Introduction (Very Short Introductions)

by David Wallace

According to positivism (or operationalism, or instrumentalism—once again, I set aside subtle differences between these positions), to understand the content of a scientific theory we need to distinguish its observational claims from its theoretical claims. And here, ‘observational’ is used in a pretty strong sense, to mean something like ‘expressible in the language of everyday objects’ or ‘testable with unaided human senses’. ‘This detector will display the number 5.228’, for instance, is an observational claim. To the positivists, non-observational claims cannot be understood independently of their observational consequences: to say, for example, ‘atoms are made up of electrons and protons’ is just to say ‘if I make this measurement I’ll get this result, if I make that measurement I’ll get that result, …’. In effect, the content of a scientific theory just is the collection of observational claims it makes: the rest of the theory is just a calculational tool to get from one set of observations to another.

positivism (operationalism instrumentalism) observational