Consciousness arises from standard (weak) emergence in physical systems, not from a radical or strong form of emergence. The paper traces emergent features through three progressive levels: life, nervous systems, and special neurobiological features, each increasing in complexity and ultimately leading to phenomenal consciousness. The formulation Life + Special neurobiological features → Phenomenal consciousness expresses this relationship. Consciousness fits the criteria of an emergent property with extreme complexity. The authors conclude that consciousness stems from an organism's personal life combined with a complex nervous system that maximizes emergent neurobiological features, and that no scientific explanatory gap exists between brain and consciousness, though an experiential or epistemic gap remains that is ontologically untroubling.
Consciousness cannot be explained solely by physics, chemistry, and biology, creating an "explanatory gap" between the physical brain and subjective experience. This paper deduces the living and neural features behind primary consciousness within a naturalistic biological framework, identifying vertebrates, arthropods, and cephalopod molluscs as taxa possessing these features. It reconstructs when consciousness first evolved and considers its adaptive value. The authors theorize that consciousness arises from all complex system features of life plus even more complex features of elaborate brains. They argue the explanatory gap persists because it stems from both life and diverse brains, requiring a complex, multifactorial account including consciousness's diversity, personal nature from embodied life, and unique neural features.