Abstract Schlick quite clearly maintains that the shift from classical physics to the theories of relativity is not necessitated by experience, but motivated by the pragmatic payoff of simplifying space-time ontology. However, there is in his work another, heretofore unrecognized argument for the revolutionary shift from classical to relativistic physics. According to this conceptual line of argument, the principles that define simultaneity and motion in classical physics fail to establish a univocal correspondence to physical quantities, and therefore must be revised, (...) along with the notions of absolute space and time that they underpin. Though these insights appear only intermittently in Schlick’s work, I will seek to elaborate on them in an effort to clarify his views on conventions within physics and the nature of revolutionary science, and to suggest that these views are invulnerable to the criticisms of pragmatic empiricists such as Quine. Content Type Journal Article Pages 1-17 DOI 10.1007/s12136-011-0131-3 Authors Steven Bland, Department of Philosophy, Huron University College, 1349 Western Rd, London, Ontario, Canada N6G 1H3 Journal Acta Analytica Online ISSN 1874-6349 Print ISSN 0353-5150. (shrink)