Consciousness and sentience are not exclusive to animals with nervous systems but are grounded in the fundamental biology of all cells. The cellular basis of consciousness (CBC) model proposes that the excitable plasma membrane, which defines a cell's internal and external domains, is the foundation for biological awareness. This article examines the biomolecular structures and processes that enable and sustain this cellular consciousness from an evolutionary perspective, arguing that unicellular organisms like protists and algae, as well as the cells of multicellular fungi, plants, and animals, all possess a primitive form of sentience rooted in general cell biology.
Efforts to solve the Hard Problem of consciousness, which search for neural correlates or trace the evolutionary emergence of consciousness, are reviewed and found wanting. The reason is that they all begin with human consciousness and treat it as a distinct type rather than as a token on the same existential continuum as other minds, committing a category error. This reveals the emergentist's dilemma: the difficulty of explaining how consciousness could spring into existence when one moment before it did not exist. The chapter anticipates criticism and offers prophylactic arguments.