Edward Callender

This paper proposes a model-specific, operational account of human consciousness. Its central definition is: a human is conscious at a particular time if and only if at least one internal or external condition is conceptually available for thought. Conceptual availability means that the condition can enter recognition, evaluation, memory, decision-making, or potential communication. Speech and immediate behavioral report are not required. The model distinguishes three levels that are often conflated: (1) affective or sensory conditions, including feelings and bodily states; (2) preconceptual awareness, in which a condition influences behavior without being available as a concept; and (3) conceptual awareness, which marks the threshold for consciousness under this account. Qualia are treated not as separate metaphysical objects but as distinguishable, conceptually accessible aspects of integrated conditions. The proposed function of consciousness is to provide a flexible decision-making control system, while language allows concepts to be shared, refined, and used cooperatively. The account overlaps with higher-order, global-workspace, predictive-processing, and functional approaches but differs by specifying an operational threshold rather than attempting to identify a universal essence of consciousness. It is explicitly limited to present-day humans; applications to artificial or hybrid intellectual entities require separate model-specific analysis. The proposal is intended to be falsifiable. Four complementary research programs are outlined: a Conceptual Availability Battery separating discrimination from conceptual access; nonverbal brain-computer-interface studies in locked-in patients; anesthetic titration combining conceptual tasks with perturbational-complexity measures; and computational ablation studies testing whether removing concept-forming capacities eliminates the flexible control functions associated with consciousness. The model would be weakened if flexible, decision-relevant cognition were reliably demonstrated without conceptual availability, or if conceptual availability were demonstrated during states otherwise robustly classified as unconscious. The purpose is not to settle consciousness by definition, but to replace an underspecified question with a precise model that generates boundary judgments, experimental predictions, and identifiable conditions of failure.

Edward David Callender is a retired mathematician and independent researcher. He earned a PhD in mathematics from Stanford University in 1959. He founded and manages the Knowledge Project, which develops operational approaches to epistemology, metaphysics, intellectual entities, and human consciousness through structured human–AI collaboration.