What al-Sadr means by the 'stability' of the mental image is this...

What al-Sadr means by the 'stability' of the mental image is this: If, for example, 1 place a pencil at a distance of one meter from me it will form an image of a specific size on the retina. If this distance is doubled, the retinal image would be reduced in size accordingly. However, al-Sadr claims, in spite of this reduction in the size of the retinal image, the mental image we have of the pencil remains stable in size. This also proves, according to him, that the mental image is immaterial.

Both of the above arguments offered by al-Sadr appear to be invalid. In the first argument, the actual size of the mental image is assumed to be the same as that of the viewed object (garden, in the example). However, when one is inside a room, the visual field presents a part of the room; when viewing a landscape, it covers a much wider space consisting of near and distant objects. When viewing the sky at night, the same visual field presents stars located at astronomical distances.

It is not logical to claim that the mental image assumes the extent of the room in the first case, the extent of the landscape in the second, and the extent of the Milky Way in the third. That the second argument is invalid will be revealed by a simple visual experiment. Every student of drawing familiar with the laws of perspective knows that objects of similar size should be drawn on a scale proportional to their distance of location.

The 'stability' of size, referred to by al-Sadr, is simply an illusion. However, the failure of these arguments does not mean that the philosophical position asserting the immateriality of the mind is indefensible. An argument that may be offered in favour of this position is the following.

If we assume the contents of the mind to be material, then it can be said that the mind should be in direct contact with the fundamental reality of matter when perceiving the data of the senses, as well as while experiencing any of its phenomena, such as thoughts, dreams, feelings, emotions, and everything else that enters the consciousness. That is, the fundamental reality of matter must be the object of the mind's direct experience if its phenomena are of a material nature.

However, we see that we do not come across any molecules, atoms or sub-atomic particles, which are what matter is composed of according to science, in any sphere of our consciousness.