Before revision: The most influential advocates of instrumentalism were the logical empiricists (or logical positivists), including Carnap and Hempel, famously associated with the Vienna Circle group of philosophers and scientists as well as important contributors elsewhere.
After revision: The most influential advocates of instrumentalism were the logical empiricists (or logical positivists), including Rudolf Carnap and Carl Hempel, associated with the Vienna Circle group of philosophers and scientists as well as important contributors elsewhere.