Platonist Roderick Chisholm has revived the Brentano thesis through linguistic analysis, distinguishing two parts to Brentano's concept, the ontological aspect and the psychological aspect. Chisholm's writings have attempted to summarize the suitable and unsuitable criteria of the concept since the Scholastics, arriving at a criterion of intentionality identified by the two aspects of Brentano's thesis and defined by the logical properties that distinguish language describing psychological phenomena from language describing non-psychological phenomena. Chisholm's criteria for the intentional use of sentences are: existence independence, truth-value indifference, and referential opacity.