Medieval Theories of Internal Senses

Abstract

Avicenna’s theory of the five external and the five internal senses and his descriptions of these had a strong impact on early medieval thought. By the ‘internal senses’ Avicenna refers to the cognitive faculties of the sensory soul other than the external senses. The organs of the inner senses are the different ventricles of the brain in which they are located. While the acts of the inner senses are associated with changes in the fine corporeal spirit, their ultimate subject is the incorporeal soul. The common sense unifies the sensations of the external senses, the imagination retains the sensations, and a third power can create configurations by combining and dividing representations in the imagination. This latter ability is called imaginative in animals and cogitative in human beings. The fourth power, which is called estimative, grasps the ‘intentions’ of things, such as their hostility or dangerousness and other harmful and useful aspects which are not perceived by the external senses. The memory is a retentive power which retains the content of the estimative power. Avicenna’s theory of the internal senses was among the leading paradigms until the mid-thirteenth century, and his conception of the estimative power was discussed right through to the seventeenth century. Another influential source for early medieval discussions was the late ancient Platonist view, also found in Augustine, in which the imagination is treated as a central immaterial power which mediates between sense and intellect; sensory acts other than perceptions are associated with the instrumental animal spirit in various ventricles of the brain.