 Drawing from Aristotelian and Neoplatonic psychology, Avicenna distinguishes between the functions of the soul by attaching them to special powers or faculties. The most relevant in this connection are sensory moving powers and internal senses: common sense, imagery (retention of sensations), estimation, memory, and imagination (separation and combination of sensory forms). Inner senses are non-perceptual apprehensive powers of the sensory soul (De anima IV.1, 1–11; IV.3, 37–40). The moving power of the sensory soul is divided into a commanding power and an executive power, the former of which is the center of emotions. The executive moving power operates through the nervous system and the muscles. It is moved by the commanding moving power, the acts of which are triggered by an occurrent evaluation of estimative power and accompanied by bodily affections as well as behavioral changes, provided that the executive moving power is also actualized. If the commanding act is strong enough, the executive power is necessarily actualized in animals, but not so in humans because they can prevent the impulse of the executive moving power by their will. The will is the moving power of the immaterial intellectual soul. Together with practical intellect, it should control the emotions (De anima I.5, 94; IV.4, 54–56, 59).