Schlick's thesis was titled Über die Reflexion des Lichts in einer inhomogenen Schicht (On the Reflection of Light in a Non-Homogeneous Medium).

[6] In 1908, he published Lebensweisheit (The Wisdom of Life), a slim volume about eudaemonism, the theory that happiness results from the pursuit of personal fulfillment as opposed to passing pleasures.

He also published Raum und Zeit in der gegenwärtigen Physik (Space and Time in Contemporary Physics), which extended his earlier results by applying Poincaré's geometric conventionalism to explain Einstein's adoption of a non-Euclidean geometry in the general theory of relativity.

[7] After early appointments at Rostock and Kiel, in 1922 Schlick assumed the chair of Naturphilosophie at the University of Vienna which had previously been held by Ludwig Boltzmann and Ernst Mach.

Early members included the mathematician Hans Hahn and, within a few years, they were joined by Rudolf Carnap, Herbert Feigl, Kurt Gödel, Otto Neurath, Friedrich Waismann, and others.

In the years 1925–26, the Thursday night group discussed recent work in the foundations of mathematics by Gottlob Frege, Bertrand Russell, and Ludwig Wittgenstein.

Eventually Wittgenstein agreed to meet with Schlick and other Circle members to discuss the Tractatus and other ideas, but he later found it necessary to restrict the visitors to sympathetic interlocutors.

Schlick and Waismann's discussions with Wittgenstein continued until the latter felt that germinal ideas had been used without permission in an essay by Carnap, a charge of dubious merit.

[11] He wrote that: It is again very deplorable that the word "necessary" has been applied to natural laws (or, what amounts to the same thing, with reference to causality), for it is quite superfluous, since the expression "universally valid" is available.

Universal validity is something altogether different from "compulsion"; these concepts belong to spheres so remote from each other that once insight into the error has been gained one can no longer conceive the possibility of a confusion.

The content, soul, and spirit of science naturally consist in what is ultimately meant by its sentences; the philosophical activity of rendering significant is thus the alpha and omega of all scientific knowledge".

In another version of the events, the murderer covered up all political causes and claimed that he was motivated by jealousy over his failed attachment to the female student Sylvia Borowicka, leading to a paranoid delusion about Schlick as his rival and persecutor.

Herbert Feigl and Albert Blumberg, in their introduction to the General Theory of Knowledge, wrote, No other thinker was so well prepared to give new impetus to the philosophical questings of the younger generation.

Though many of his students and successors have attained a higher degree of exactitude and adequacy in their logical analyses of problems in the theory of knowledge, Schlick had an unsurpassed sense for what is essential in philosophical issues.