2.222 Its truth or falsehood consists in the agreement or disagreement of its sense with reality.

Theory of truth? This contrasts, says Proops (p. 59), with Russell’s view in the Principles, according to which truth and falsity are indefinable properties belonging to propositions, the latter being complexes which he found it difficult to define (see “The Nature of Truth” (from 1905) in Russell’s Collected Papers Volume IV, p. 503, quoted in Proops on pp. 59-60, note 157).