 As mentioned above, Hartmann’s philosophical style presented a strong contrast with that of his peers. Philosophy for Hartmann was a critical, systematic, analytical investigation into the fundamental problems of existence. It meant rejecting ready-made standpoints, ungrounded speculation, system-building, and extreme, improbable conclusions. He claimed that “the prerequisite of systematic thinking is the purity of the philosophical ethos,” which is “perseverance in investigation, patient waiting, capacity to remain suspended in uncertainty,” the “genuine dianoetic virtue of the philosopher” (S 5–6). Utilizing the methods of phenomenology and aporetics before passing to theory, critical ontology is the desideratum for systematic philosophy (S 51). Philosophy is not about committing to a single monolithic standpoint or theory and looking at every human problem through its narrow lens. It is not system-building speculative idealism (German Idealism), an epistemology of the sciences (positivism), logical idealism (Marburg Neo-Kantianism), transcendental phenomenology (Husserl), universal hermeneutic phenomenological ontology (early Heidegger), theory of worldviews (Dilthey), philosophy of life (Bergson), or metaphysical personalism (Scheler). All of these theoretical standpoints invariably commit the chief fallacy, identified by Hartmann, of attempting to use one set of categories to explain the entirety of the real world (Peterson 2012). Hartmann’s articulated and robust categorial ontology leaves room for the fantastic diversity and abundance of the world, provides a satisfying nonanthropocentric humanist account of the place of humankind in the cosmos, and has even inspired a recent comprehensive approach to environmental philosophy (Peterson 2020). There is much to be learned from Hartmann’s work, and this article only scratches the surface.