Psychological research engages with manifold phenomena, including as diverse events as verbal self-descriptions, neural activity, and societal changes. Still, the discipline owns a proper perspective onto being, identifying a genuinely psychological aspect in life. This tacit subject-matter of the discipline has been the topic of recurrent discussions in theoretical psychology, but no ultimate answer could be found. Hence, the problem of subject-matter arises. To face it, theoretical psychology requires not only knowledge about its history but also a systematic approach. This approach encompasses a methodology unlike empirical procedures, consisting of meta-methods, for instance, hermeneutic philosophy of science. Such meta-methods reveal that the problem of subject-matter partakes in a foundational hierarchy of problems which reunites psychology with philosophy. When addressing the problem of subject-matter, it becomes necessary also to explore the problem of reality.