The so called "sense organs" are parts of the brain. Bodies are, in fact, perceptual brains.
Visual reasoning is an analytical method that employs human perception in order to communicate, problem solve and create.
Drawing is thinking, in the same way (though likely not through the same cognitive means?) writing is thinking.
According to evolutionary epistemology, biological adaptations are one form of knowledge, and science is another; both are produced by the processes of blind variation and selective retention (Campbell 1975 [in American Psychologist¸ 30, 1103-26]).
Uses of visual reasoning
Problem solving; examples include engineers who sketch a solution on the back of an envelope.
Visualizing the behavior of complex systems over time.
Metaphor.
Education, especially for interdisciplinary and critical studies
Neglect of visual reasoning
Visual reasoning is, well, visual; if there are different perceptual-epistemological domains -- different ways of knowing, as in visual and verbal -- then neglect of visual reasoning is a violation of civil rights.
One of the problems we've noticed is that visual reasoning appears to be dominated by engineers and architects. Even designers, who think visually for a living, rarely analyze what it is they do in ways that would enable others to use their techniques. Exceptions abound, of course; consider the example of Edward Tufte.
While scientists use visualization technologies (pencils, computers) all the time, rarely is the art of scientific visualization investigated scientifically. Rather, the knowledge that could contribute to a pedagogy of visual reasoning is locked in separate "silos," at best, or left completely untheorized (graphical skills are a talent). In other words, graphic artists may work for scientists but scientists rarely work for graphic artists--or the graphic arts.
The Perceptual Economy
We see things all the time we don't believe, and accept as truth images we know are lying.