Extramission VS Intromission

Figure 1. The description of extramission theory [2]

Figure 2. The description of intromission theory [3]

Many of us do not appreciate our capabilities of seeing things. We can see everything we want, under

certain circumstances, without being intrigued by how complicated it is to see. I believe that this is

mainly because we already possess an extraordinary optical apparatus set that allows us to see since we

came to this earth. Whenever we see, we often think that being able to see is what is supposed to be, is

taken for granted, why so much bother? Yet, I believe that no one in this world would sacrifice the

capabilities of seeing over other senses. Without vision, we cannot recognize our lover's face. Without

seeing, we can no longer enjoy the beauty of rainbow, sensing the freshness of the nature, reading

books, doing visual analysis in this writing project, and the list continues infinitely. More importantly,

the result of not being able to visualize images must be devastating. It does not only affect our visual

perception in the brain, but as well as our psychological states that seems to be the confounding

variables to the complexity of social life. Only those who have iron will such as Helen Adams Keller and

Louis Braille are able to conquer and win the world in the midst of their darkness.

Figure 1 above depicts the archaic view of the process of seeing. This view is well known as the

extramission theory of vision, was postulated by pre-Socratic Alcmaeon of Croton and was elaborated by

Plato around 400 BC. In this perspective, we can sense the visual object because our eyes possess "fire"

within that comes out of the eyes and merges with daylight to produce a "single homogeneous body"

that serves as an instrument for detecting and reporting visual object [1]. This homogeneous body then

received by the soul and hence we perceived the sense of seeing. Concretely, as depicted on figure 1,

the "visual fire" acts like a hand that touches an object. Thus the visual fire touches the "body of vision"

in such a way that our soul grasps the shape of the object. However, this fire must collaborate with the

sunlight because without light, the fire cannot touch the body of the visual object. Essentially, the

extramission theory claims that something must be done to the visual world in order to "touch" the

visual object. This obscure line of thought was easily accepted at that time given the strong influence of

Plato.

The opposite of extramission theory is called intromission. In this regard, unlike extramission, something

the visual world must do to us in order to see things. This view turned out to be true and had been

developing through time because, believe it or not, until now no one can truly understand what seeing

is. The process of seeing is so convoluted that involves many fields of science, especially optics and

neuroscience.

Without being engaged in the intricate process of seeing in the perspective of intromission, figure 2

depicts the emerging concept of this theory. As mentioned earlier that something must come to our

eyes so that we can grasp the object. And that thing is called light which is reflected by the object and

received by our eyes. On the picture, there are four people (C, D, E, and F) seeing a dragon that has

length from A to B flying above them. Each person sees the dragon with different angle and field of

view. Whether a person can see the whole body of the dragon, the picture tells us that the light rays

that come from every point of the dragon's body from A to B have to be focused into one point, that is,

C, D, E, and F. A person can still see the dragon wholly although he or she has a small angle field of view,

but that person must stand at a longer distance (person F). However, the drawback of seeing at longer

distance is that the person in charge may not see the dragon clearly as depicted by less number of light

rays. On the other hand, if a person sees the dragon at a small distance, he or she must have big field of

view (person D) so that the whole light rays emanating from the dragon can be gathered. Seeing the

dragon from a small distance gives the observer a clearer image as shown by greater number of light

rays focused at point D compared with at point F.

References:

[1] Charles G. Gross, "The Fire That Comes from the Eye", The Neuroscientist, 1999

[2] http://nivea.psycho.univ-paris5.fr/FeelingSupplements/AncientVisions.htm

[3] Jennifer M. Groh, "Making the Space - How The Brain Knows Where Things Are", The Belknap Press

of Harvard University Press, 2014