Interpreting the Principle ‘The Reality of Things Is Truly Existing’ in the Context of Quantum Theory: A Study on al-Ghazālī and Fakhr al-Dīn al-Rāzī

In classical kalām literature, the principle “the reality of things is truly existing” stands as one of the most fundamental premises grounding both the reality of the external world and the possibility of human knowledge. It rests on the assumption that entities and phenomena possess a stable, mind-independent ontological foundation. This provides the necessary basis for the objectivity of knowledge and for the intelligibility of existence through reason. The mutakallimūn, particularly in response to the Sophists’ claims that “truth does not exist” or “knowledge is impossible,” developed this principle through logical refutations. For them, the fixity of reality is the essential criterion for truth and the foundation of human cognition’s reliability; if reality were not Truly Existing, knowledge would lose both its value and its objectivity. This framework assumes that human knowledge can access a real and intelligible domain through the cooperation of the senses and reason. The senses convey data from the external world, while the intellect organizes and interprets these data to generate knowledge. Thus, the truly existing reality ensures the epistemological and ontological stability upon which valid knowledge depends. Modern quantum mechanics, however, has challenged this classical perspective by breaking with absolute determinism and redefining the relationship between observation and reality. Concepts such as Heisenberg’s uncertainty principle, Bohr’s complementarity, and Schrödinger’s superposition have undermined the assumption that reality exists as a truly existing essence independent of context and measurement. At the quantum level, being is no longer a static substance but a phenomenon emerging within networks of probability, relation, and observation. Accordingly, this study examines the kalām principle of truly existing reality within both historical and conceptual dimensions, reinterpreting it in light of the epistemological insights offered by modern physics. It focuses particularly on al-Ghazālī and Fakhr al-Dīn al-Rāzī, whose ontological analyses reveal a layered conception of existence paralleling the contextual and probabilistic nature of quantum phenomena. Thus, the notion that “reality is truly existing” is reconsidered not as a rigid metaphysical principle but as a dynamic framework linking being, knowledge, and perception. Ultimately, this synthesis suggests a complementary, rather than contradictory, relationship between the metaphysical constancy of kalām and the probabilistic realism of quantum mechanics—revealing truth as both enduring and multifaceted.