A third realm ontology? Naṣīr al-Dīn Ṭūsī and the <italic>nafs al-amr</italic>.

The standard interpretation of Avicenna's correspondence theory of truth posits that propositions either correspond to what exists extramentally or otherwise their truthmaker is mental existence. An influential post-Avicennian philosopher, Naṣīr al-Dīn Ṭūsī (d. 1274) points to the insufficiency of the above division of propositions and their respective truthmakers. He mentions the possibility of conceiving false propositions, such as ‘One is not half of two’ and postulates the necessity of the existence of another truthmaking domain for their true counterparts which he calls <italic>nafs al-amr</italic>. It is where objective and timeless entities, such as mathematical propositions, are located. While some claim that Ṭūsī's identification of this domain with the first Separate Intellect is a testimony to his Avicennian convictions, Ṭūsī's solution is a conspicuous departure from Avicenna that not only helps him remedy the insufficiency of Avicenna's theory of truth but is consistent with his critique of Avicenna's theory of God’s knowledge. [ABSTRACT FROM AUTHOR]