This article provides a critical examination of the classical problem of the nature of body in Islamic philosophy. The traditional dichotomy between substance, considered as the bearer, and extension, considered as an accident (predicate), has confronted philosophers with the problem of the void (vacuum); since the void is defined as an extension without a subject, it is deemed an impossibility. Employing an analytical-critical approach, this research challenges the prevailing views concerning the reality of the body, ranging from the atomistic theories of the Mutakallimun (theologians) to the Peripatetic theory of matter and form (hylomorphism). The main hypothesis of this paper proposes a conceptual revolution in this context: extension (here referring to the three dimensions) is not an accident, but rather is itself the simple and fundamental substance of the material world. Accordingly, body, space, and vacuum are not three distinct realities, but three names for a single reality termed “three-dimensional substantial extension.” This article demonstrates that this redefinition not only fundamentally dissolves the classical problem of the void, but also offers a coherent, unificatory explanation for the multiplicity of material bodies based on the principles of Transcendent Theosophy (Hikmat al-Muta’aliyah)—particularly the gradation of existence (Tashkik al-Wujud) and substantial motion (Harakat al-Jawhariyyah). Ultimately, it paves the way for a constructive dialogue between philosophical ontology and the modern understanding of physical reality.