The common man is apt to claim that one thinks in images -- that mental images constitute the very fabric of thought itself. The philosopher, even the ardent imagist, is not as quick to accede.
This is evident if one considers three issues of central historical importance regarding the role of images in thought. These are
It turns out that there is no consensus view on these questions. There is a convenient way to map out some possibilities, however. If all of these questions were answered affirmatively, this would be called Strong Imagism, or the view that ideas are mental images and that thinking consists entirely of operations using them. The common man, at least prior to reflection, is likely to believe in Strong Imagism. This is not, as H. H. Price pointed out, a view any philosopher actually seems to have held, though many philosophers have held some portion of it and some moderns (e.g., Berkeley and Hume) have been accused of endorsing it completely. If all the all the questions are anwered in the negative, this forms the basis for what I call Strong Descriptivism.
There are some important historical answers to some of these questions that appear over and over again. Since a complete treatment of the topic lies beyond the scope of this introductory material, this introduction will simply list a few of these historically-important answers. Many contemporary philosophers and psychologists, particularly those of the descriptivist school, have offered substantial reasons why images can have no have no content and reasons why they can have no role in thought.
Aristotle has the most unequivocal answer to the question of the necessity of images in thought. He states
To the thinking soul images serve as if they were contents of perception... That is why the soul never thinks without an image. (On the Soul, 430b14-17)
Descartes held precisely the opposite view about the necessity of thought images. He argued that imagery is not necessary for understanding. A piece of wax may appear to us in various shapes, sizes, and even as a solid or a liquid, yet still remain the same substance. No specific image of the wax can correctly represent our understanding of it as a substance that remains the same through multiple physical incarnations. Descartes concluded that it is quite possible to understand what something is without being able to form an image of it.
The the thesis of "general ideas," usually attributed to Locke, is extremely important to all discussions about the role of images in thought. The notion of general ideas (generalized images) has been used to show how thought images differ from other images. The locus classicus of Locke's reputed invention of the indeterminate image is the following:
For example, does it not require some pains and skill to form the general idea of a triangle (which is yet none of the most abstract, comprehensive, and difficult); for it must be neither oblique nor rectangle, neither equilateral, equicrural, nor scalenon; but all and none of these at once. (Locke, 1690, Bk. IV, Ch. 7, para. 9)
The thesis of general ideas has proven resilient in both philosophy and psychology, because of its intuitive simplicity: thought images are different from other images and they need to be different because form follows function. Thought images need to represent general terms, therefore they are general in form.
If the thesis of general ideas does not place particular restrictions on the way in which our thoughts may be structured by the mental images, it contrasts sharply with another tradition in the history of philosophy that does. Suppose we accept it as a principle that since all images originate in perception as particulars, the mind has only these to work with, and no new natures can be introduced. Both Hobbes and Hume attempted to follow the implications of this thesis. Both identified thought with a sequence of "ideas" (both sounds and images) in the mind. All these were determinate particulars, differing only from the original perception in degree of intensity and the combinatorial possibilities supplied by the laws of association.
Hume argues, for example, that we have no original perceptual image of causality, only the regular succession of one kind of events followed by another kind of events. Therefore we have no authentic conception of causality. We have no direct experience of an image of the soul or of God, therefore the existence of these as independent substances is a dubious proposition at best. Another example: consider a mathematical point. Hume asks, what image can we form of it? Hume's introspective evidence is that a point may be imagined as a small dot. He argues such an image has no proper size at all. A small point can be imagined as easily as a large point, and no matter what size the image of a point is understood to be, the image does not admit of division and still remain as an image of a point. Since our image of a point does not admit of division, Hume reasons, there is no such thing as an infinitely divisible magnitude. The properties of the image of the smallest imaginable magnitude do not allow this conception. Mathematicians and philosophers, according to Hume, are therefore wrong when they appeal to our understanding of our innate conceptions of mathematical realities, for this is sheer contrivance.
In my work, I argue that the shift to thought imagery involves more than just an intentional shift (a shift in "attitude") directed toward a single presentation. Locke and Hume are wrong when they assert that thinking abstractly essentially involves our reflections on or intuitions about a single image. This is particularly evident in the case of Hume's example of the mathematical point: Hume's conclusion that there is no such thing as an infinitely divisible magnitude is evidently false, and it is his supposition that our reasoning about such things is necessarily constrained by the apparent properties of the image that causes him to arrive at this false conclusion.
Part of my view is that thinking using images involves a shift in the rules of mental engagement. While imagination is important in that it may be used to free one's self from previous suppositions, thought tends to re-impose requirements. These "requirements" may be what is already known about the rules of mathematics, physics, or (perhaps) human nature. Einstein may imagine riding a light beam, but he is not thinking about it until he attempts to deduce the consequences of imagined actions under these conditions as they would apply to the actual world of physical laws. Descartes can imagine that his mind exists without his body, but when he considers this supposition in the light of what God and nature teach him, he cannot actually think this to be true (Meditation VI). Thought images, then, give rise to non-imaged thought processes. These processes involve deriving the reasoned consequences of situations that were symbolically indicated by images. This does not solve the age-old debate about the necessity of imagery in thought, but, I believe, we must at least make this distinction if we are to solve it.
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