For instance...

For instance, the human being exists in external reality and, being a substance, it exists there without the need of a subject (mawdû). As a body (jism), it is valid to ascribe to it three dimensions. Moreover, as a ‘living thing,’ ‘animal’ and ‘human being,’ it manifests the properties and characteristics of these genera and differentiae. However, the human being existing in the mind, though it fulfils the definition of ‘human being,’ does not possess any of these external properties.

However, some of them hold that what we know (the so-called ‘mental existence’) is a resemblance (shabah) of the quiddity, not the quiddity itself. It is an accident (‘arad) and a quality (kayf) subsisting through the soul (nafs). In its essence (dhât) it differs from the external thing known, only resembling it and representing some of its characteristics. It is like the picture of a horse painted on a wall that represents the horse existing in external reality.

Such a view in fact boils down to a denial of the possibility of knowledge, for it totally closes the door to the knowledge of external reality.” Some others have been led to deny mental existence altogether, holding that the soul’s knowledge of an external object is a special relation between it and the soul. Such a position is refuted by the knowledge of anything non-existent; for the soul’s relation to something non-existent is meaningless.

Those who believe in mental existence have advanced the following arguments in its favour. (i) We make affirmative judgements concerning non-existents, as about a “sea of mercury,” or posit such propositions as “The co-existence of two contradictories (naqîdayn) is different from the co-existence of two contraries (diddayn)” and the like. Affirmation means to posit the subsistence of something. The affirmation of one thing (B) in regard to another thing (A) is subordinate to the subsistence of A.

Hence subjects that are non-existent [in external reality] have an existence. Since they have no existence in external reality, they must have an existence somewhere else, that is, the mind. (ii) We conceptualize certain notions possessing universality (kulliyyah), such as the universals ‘man’ and ‘animal.’ A concept is a rational pointer that has no significance unless it points to an existent.

Since the universals qua universals do not exist in external reality, they must have existence somewhere. That somewhere is the mind.