A living organism endowed with a highly evolved nervous system interacts with its environment through a chain of processes in which we may distinguish representational, doxastic, appetitive and volitional aspects. Representation is the outcome of on-line analysis and synthesis of sensory input as well as endogenous fabrication based on past experience and extrapolation to imaginary states of affairs in the world. Doxastic aspects relate to the complex of beliefs, explicit or dispositional, independent of
their truth. Appetitive and volitional components merge into the execution of purposeful action.