  To Carnap, the deeper problem was that, by the lights of his 1934 work on The Logical Syntax of Language, affirmations are not well-formed expressions at all. Earlier, in his (1932a) contribution to the protocol sentence controversy, Carnap’s treatment of observation was based on the Thesis of Metalogic, the idea that all philosophical contentions (which are not nonsense) are metalinguistic claims about linguistic expressions and their logical (particularly syntactical) properties (Carnap 1932a, 435n). The function of the Metalogic Thesis was to isolate pseudo-theses or statements which seem to concern substantive matters but are really concerned with logical or linguistic matters. Of course, these pseudo-theses became known as ‘pseudo-object sentences’ and their analysis became a centerpiece of Carnap’s Logical Syntax-era philosophy (Carnap 1937, Sec. 74). And the Metalogic Thesis, together with the Principle of Tolerance (which asserts that the choice of any specific language is a conventional decision), formed the principal theses of Carnap’s philosophy of logic in the Thirties (Carnap 1937, 51–2). Otto Neurath, who endorsed the Metalogic Thesis and the Tolerance Principle, drew the obvious conclusion that Schlick’s defense of the correspondence conception of truth, explicated by his analysis of affirmations, committed him to the recognition of “the one, true reality” and “the real world” (Neurath 1983, pp. 106–8; Uebel 2007, Sec. 8.2). In short, Schlick’s foundations were spelled out in nothing more than philosophical pseudo-statements.