In the dialog Sophist, written in 360 BC, Plato wrote:
My notion would be, that anything which possesses any sort of power to affect another, or to be affected by another, if only for a single moment, however trifling the cause and however slight the effect, has real existence; and I hold that the definition of being is simply power.
# Neurobiology Some science of consciousness - qz.com
Integrated information theory (IIT) attempts to explain what consciousness is and why it might be associated with certain physical systems. Given any such system, the theory predicts whether that system is conscious, to what degree it is conscious, and what particular experience it is having (see Central Identity). According to IIT, a system's consciousness is determined by its causal properties and is therefore an intrinsic, fundamental property of certain causal systems - wikipedia