The present article seeks to reconstruct the modern and contemporary discourse on consciousness, reading the concept of consciousness as a boundary concept. It compares the tension between third-person explanation and first-person experience in the context of the hard problem of consciousness. The article does not justify the non-physicalist views of substance dualism, mysterianism, and anti-scientific skepticism. It suggests, on the contrary, that historically consciousness has served, time and again, as a limit case for the closure of explanations. Consciousness is a boundary concept. A concept functions as a boundary concept for a domain of inquiry when it denotes both an object within the domain and a condition of the inquiry itself. Any candidate explanation of phenomenal consciousness either abstracts from first-personal givenness (leaving the explanandum as residue) or takes that givenness as data (in which case the explanans covertly contains what it purports to explain). Contemporary theories of consciousness are broadly divided into reductive (or third-person, objective) and non-reductive (or first-person, subjective). They try to maintain consciousness as either part of the physical world or as a non-physical entity. We test the thesis against the principal contemporary programs — global workspace theory, integrated information theory, higher-order theories, predictive processing, illusionism, and Rus¬sellian monism — and derive a set of constraints on explanatory pluralism from it. We show that Husserl’s phenomenological method and theory of intentionality place consciousness as a boundary concept that manifests the very distinction between mind and world.

Received 18 May 2026. Revised 15 August 2026. Accepted 30 September 2026. Published online 15 November 2026