This text explores the philosophical distinction between monism and pluralism. The author critiques the traditional classification based on the concept of substance, viewing it as unsustainable and obsolete. Instead, the focus shifts to the dialectical relationship between multiplicity and unity. While everyday experience confirms the existence of multiplicity, the text argues that such multiplicity is only possible through the existence of specific units. These units cannot be recognized solely through sensory experience but require a broader involvement of critical thinking capable of self-reflection. A crucial development in this intellectual process is the differentiation between "true" and "false" units. While false units are identified as mere aggregates or heaps, true units represent distinct individuals that are not necessarily simple or indivisible. The reflection thus moves the focus from a metaphysics of substance to an analysis of the nature of unity and the whole within the sphere of thought. This approach provides a new perspective on the structure of reality and its constituent elements beyond traditional ontological categories.