After having rigorously defined perception and imagination as the two great irreducibles of consciousness, J.P. Sartre refers, in his L'Imaginaire, to intensions vides(empty intentions), which do not posit new objects, but determine the existing objects in relation to their diverse aspects not hitherto perceived. For example, it is a matter of course that this ashtray beside me has an underside and that it is put on the table so that the underside comes actually in contact with the surface of the table, and that this underside is of white porcelain etc.. What is aimed at is by no means the invisible aspect of the thing, but its visible aspect in relation to its corresponding invisible aspect. That is, the surface of an ashtray, in so far as the structure of its surface implies the existence of an underside. As Sartre describes that it is evident that these intensions give perception its plenitude and richness; in this he almost shares Merleau-Ponty's view. Merleau-Ponty, however, proceeds to describe that, since things and my body are made of the same material, the body's vision must somehow emerge among things, or rather that things' manifest visibility is lined with a hidden visibility in the body.
Here is the problem of space, which may be called the visual "action through the distance" between things and me. If we consider both to be made of the same material, as Merleau-Ponty does, the distance is nothing but what is on a continuous surface. The space between my eyes and things, however, is the transcendent distance which cannot be shown as being on a plane. Their confrontation cannot be explained, for example, by the distance between my eyes and my hand. The space meant here is a sort of depth across the boundary between mind and body; the process of transfer or permeation between the two textures which compose the two aspects-external and internal-of a being. This opaque depth is also a kind of sense of volume in which my mind and body abide, and that is really my being. Tactile sensation, in this sense, does not open my being externally, but fills it up internally and ensures its unity with things.
However, ultimately I cannot touch my mind. Tactile sensation offers the sense of volume of my body above all things, and locates it in the material world. It is the zero of the world, a negative place opened in it, my surest dwelling. When this material texture of my being is transferred by the movement of my hand to an other thing(a sculpture, natural object, other's body etc.) and is thereby turned positive, then the miraculous self-recognition by tactile sensation is attained.
If the texture of my being is touched and realized outside my body, as an other being and as a part of myself(my double) at the same time, the world is already a part of myself while I am a part of the material world, and I experience the existence of "intermediate subject" between myself and the other being.
As with Impressionist paintings, light was transposed from nature to the material of colours, so with photography and other various visual images which have been so far developed, colours have been transposed from material to light, from tactile depth to simply visible surface or even less real, dispersing optical phenomena.
Since we live as physical beings essentially within our own body, our conception must be based on perception, but the perception of light by visual images may be called "la vision vide"(empty vision), which does not directly correspond to the material world.
In the artificial world of today, where "la vision vide" constitutes most of my perception, I am able to obtain abundant visual information of the world, and am also able to highten my ability to respond to visual symbols, but my primitive, organic perception supported by the total functions of my body tends to be neglected, and sometimes even distorted.