One of the leading figures of Logical Positivism, Moritz Schlick, wrote a well-known article “On the Foundations of Knowledge”, edited in English by Sir Alfred Ayer in 1959, in which he proposes Konstantierungen, also known as affirmations or confirmations in English, to play the part of the much sought-after indubitable and incorrigible foundation of personal belief. In the present article I will oppose this view via the perspective of confirmations in their linguistic nature, a trait that renders Konstatierungen untenable both as sentences in Language of Thought (Fodor, 1975) – where it is thought that is linguistic, and natural language is but a means for expressing it-, and as occurring in natural languages due to the obligatory phenomenon of grammatical evidentiality in many world languages.One of the leading figures of Logical Positivism, Moritz Schlick, wrote a well-known article “On the Foundations of Knowledge”, edited in English by Sir Alfred Ayer in 1959, in which he proposes Konstantierungen, also known as affirmations or confirmations in English, to play the part of the much sought-after indubitable and incorrigible foundation of personal belief. In the present article I will oppose this view via the perspective of confirmations in their linguistic nature, a trait that renders Konstatierungen untenable both as sentences in Language of Thought (Fodor, 1975) – where it is thought that is linguistic, and natural language is but a means for expressing it-, and as occurring in natural languages due to the obligatory phenomenon of grammatical evidentiality in many world languages.