What did Georg Wilhelm Friedrich Hegel mean by the idea that substance must become subject?

When Georg Wilhelm Friedrich Hegel declared that "substance must become subject," he was articulating a central goal of his philosophical system: to reconcile the strengths of classical and modern philosophy.1

Historically, Hegel argued that Greek philosophy successfully grasped the concept of substance—the objective, underlying reality of the world—but lacked an adequate understanding of modern subjectivity. Conversely, modern philosophy, beginning with Descartes, prioritized the subject as the starting point of inquiry but struggled to develop a robust account of objective truth, often falling into "subjectivism" or solipsism.1

By asserting that substance must become subject, Hegel meant that reality (substance) should not be viewed as a static, external entity, but as a dynamic, rational process that realizes itself through consciousness and history. He sought to bridge the gap between ontology and epistemology, arguing that the rational structure of the world is not merely something the mind imposes, but something it discovers as it unfolds through the dialectical process.21