  Within a few years, Schlick wrote the essays which are characteristic of his early Positivist thought. The first one, “The Turning Point in Philosophy,” appeared in 1930. It contains an early version of the thesis that the function of philosophy is the analysis of meaning (Schlick 1979b, 154–160). A more decisive article was the 1932 essay, “Positivism and Realism”, a classic piece which shaped some of the most characteristic philosophical work to emerge from the Positivist tradition (Schlick 1979b, 259–284). Schlick interprets the verifiability principle strictly, by spelling out verification in terms of sensible experience, but at the same time broadly, construed to admit any logically conceivable circumstances of verification (like the future verification of mountains on the far side of the moon). The basis of this principle, Schlick argues, is to be found in scientific practice. He cites Einstein’s analysis of “simultaneity” in Special Relativity as his primary example, an illustration which would become a staple of Positivist lore. Schlick also mentioned Planck, who acknowledged that experience was the source of scientific knowledge.  Schlick called the philosophical view founded on this principle, “Logical Positivism”, using the designation introduced by A. E. Blumberg and Herbert Feigl (Blumberg and Feigl, 1931). As Schlick explained it, Logical Positivism is essentially a realist epistemology, like the one developed in Schlick’s General Theory of Knowledge, which shares little with the classical positivism of  Auguste Comte,  Ernst Mach, and Hans Vaihinger. Schlick’s principal conclusion was that Logical Positivism never denies the reality of material objects but, rather, equates physical reality with the lawfulness of experience. Unfortunately, Planck, who had always supported Schlick in the past, misunderstood the essay, interpreting it as a polemic for Machian positivism, and harshly condemning it (Planck 1932).