 Ramsey 1926 introduced the by-now standard distinction between logical and epistemological contradictions (but see already Peano 1906, and section 3.3.1 of this entry). While logical contradictions involve mathematical or logical terms, like class, number, and hence show that our logic or mathematics is problematic, semantical contradictions involve, besides purely logical terms, notions like “thought”, “language”, “symbolism”, which, according to Ramsey, are empirical (not formal) terms. Hence these contradictions are due to faulty ideas about thought or language and they properly belong to “epistemology”.