To quote from Wikipedia:
Biological Naturalism states that consciousness is a higher level function of the human brain's physical capabilities.
Biological naturalism is a monist theory about the relationship between mind and body (i.e. brain), and hence an approach to the mind-body problem. It was first proposed by the philosopher John Searle in 1980 and is defined by two main theses: 1) all mental phenomena from pains, tickles, and itches to the most abstruse thoughts are caused by lower-level neurobiological processes in the brain; and 2) mental phenomena are higher-level features of the brain.