The “inconsistent tetrad” refers to the four propositions commonly used in the philosophy of mind to address the issue of the mind-body relation. As the name suggests, although each of these propositions may individually be true, only three of them can be true at the same time, while one must always be false. For instance: 1) The soul is a non-material substance; 2) The body is a material substance; 3) The soul and body are in relation to each other; 4) The relationship between material and non-material entities is impossible. Throughout the history of philosophy, different philosophers have provided various solutions to this problem. Dualists, who believe in the non-material nature of the soul, reject the fourth proposition, which denies the possibility of the relationship between material and non-material entities. In contrast, proponents of physicalist theories attempt to resolve the issue by materializing the soul.
This paper attempts to analyze the inconsistent tetrad from the perspective of the 17th-century Safavid philosopher Sadr al-Din Shirazi. After explaining the nature of the inconsistent tetrad, the paper discusses Shirazi’s concept of the soul. It then examines which propositions, from the perspective of his theory of the soul, are likely to be true and which are likely to be false. The conclusion emphasizes that, according to Shirazi’s theory of the soul, which is “corporeal in its origination, but spiritual in subsistence,” the soul and body represent the only ontological unity that evolves from matter to spirit. Unlike the dualist or physicalist viewpoints, the Shirazi perspective offers not a singular solution, but multiple possible solutions to this problem.