 A more careful statement of what was probably much the same doctrine is provided by Avicenna. Concepts like “horse”, “animal”, “body”, correspond to entities in the real world, entities which can have various properties. In the realm of the mental, concepts too can acquire various properties, properties they acquire simply by virtue of existing and being manipulated by the mind, properties like being a subject, or a predicate, or a genus. These are the subject matter of logic, and it seems it is only mental manipulation that gives rise to these properties.