Ibn Sīnā, instead of employing the expression “its existence in the soul” used by Aristotle and al-Fārābī, adopts the expressions “its existence in the mind” and “existent in the intellect.” Through this distinctive vocabulary concerning the mode of mental existence as opposed to objective existence, he rendered a major service to later philosophers that led this discussion on mental existence to be presented independently. Expressions such as meaning, definition, representative, correlate, form, effect, exemplar, reality, and intelligible enabled a clear articulation of the identity of mental existence and prepared the ground for addressing the famous problem of mental existence. By introducing the notion of meaning, Ibn Sīnā took a decisive step toward resolving this problem and provided later philosophers, especially Mullā Ṣadrā, with a conceptual key for its solution. One of the most significant features of his works is his attention to philosophical concepts. While philosophers generally connected the issue of mental existence with quiddative concepts, holding that only these quiddative concepts possess mental existence, Ibn Sīnā, by appealing to examples such as motion and non-being in his discussions, opened a new path in this regard. He also systematized the arguments for the existence of mental existence and articulated the notion of the verity proposition (qaḍiyya ḥaqīqiyya) in his writings.