The manifesto of the Circle was Wissenschaftliche Weltauffassung: Der Wiener Kreis (The Scientific Conception of the World: The Vienna Circle) was published in 1929 and translated by Otto Neurath (1882–1945) in his Empiricism and Sociology (1973). The manifesto proclaims that the scientific world-conception of the Vienna Circle is distinguished “essentially by two features. First it is empiricist and positivist: there is knowledge only from experience. Second, the scientific world-conception is marked by the application of a certain method, namely logical analysis.” Logical analysis is a way of using symbolic logic to determine whether sentences or their components refer to experience. Many logical positivists were also phenomenalists.

Not to be confused with phenomenology, phenomenalism is the empiricist doctrine that sense data, or the sensory organ’s impression of perception, could be used to explain the meaning of sentences about perceptual objects. Some believed that perceptual objects themselves, such as a computer, a desk, or a car, could be reduced to sense data. This last ontological version of phenomenalism would involve a general commitment to philosophical idealism or the doctrine that the only things that are real are mental phenomena.