Figure 6.4
If we look at the drawing, we recognize Saturn and its rings, but simply because we have already seen other elaborated representations, of which this sketch anticipates a few pertinent features (a globe with an ellipse around it—and it’s up to us to see perspective in a sketch that does very little to suggest it). Note that Galileo did not see this perspective, otherwise he would have spoken not of two semiellipses but of an elliptical band.18 Galileo still saw a kind of Mickey Mouse, a face with two large ears. But it cannot be denied that this third drawing is more like successive images, even photographic ones, of Saturn at its point of maximum inclination. In any case, on a morphological level it corresponds to the cognitive type of Saturn possessed by a person with average knowledge. Note that (due to the claimed coincidence between cognitive type and nuclear content or Immediate Object) if asked to represent Saturn, a person without particular graphic talents would today make a drawing fairly similar to Galileo’s, probably completing the lower part of the two ellipses so that the ring passes in front of the globe.
In the light of Galileo’s efforts, one is led to think that it is not the construction of the cognitive type that precedes the drawing; if anything, it follows it:
Saturn-in-itself → Saturn on the lens → Drawing → Cognitive Type
It is only by trying to fix on paper the essential features of what was being received (in this stage, clots of Firstness, an uncoordinated sequence of stimuli) that Galileo gradually began to «see,» to perceive Saturn and to construct a first hypothetical cognitive type. Which is also what I was trying to say in A Theory of Semiotics with regard to radical inventions.19
Having said all this, we have still said nothing about the second element of the chain, Saturn on the lens. From a semiotic point of view, it would seem to be a negligible phenomenon: the telescope constitutes a channel through which Galileo received a series of stimuli, as he would have received them had he boarded a spaceship and traveled to a point sufficiently close to Saturn.
But it is precisely this «as if» that demands some additional reflection (and never was metaphor so literal). Not so much to gain a better understanding of perception as to return yet again to the phenomenon of hypoicons.
6.10 Prostheses
Normally we give the name prosthesis to any apparatus that substitutes a missing organ, but in a broad sense prostheses are all apparatuses that extend the range of action of an organ. When people are asked where they would like to have a third eye, were this possible, they usually provide rather uneconomical responses: some would like one on the nape of the neck, others on the back, without taking into account that whereas this would certainly allow them to see what is going on behind them, it would not help with regard to an infinity of other places into which they often wish they could see: the top of the head, behind the ears, on the other side of a door, or inside the hole into which their key has fallen. The correct answer, in the sense that it is the most reasonable one, would be: on the tip of the index finger.
It is obvious that in this way we might extend the range of our vision to the maximum, within the limits of our bodily range of action. 20 Well, if we had an artificial eye that was as maneuverable as our index finger, we would have an excellent extensive prosthesis with an intrusive function into the bargain (in the sense that it would go see not just in places where the eyes could look if we turned our head or moved but also into places where the eyes cannot penetrate).
Substitutive prostheses do what the body used to do but for one accidental reason or another no longer does: such devices include artificial limbs, walking sticks, spectacles, pacemakers, and hearing aids. Extensive prostheses, on the other hand, extend the natural action of the body: such devices include megaphones, stilts, and magnifying glasses, but also certain objects that we do not habitually consider extensions of our body, such as chopsticks or pliers (which extend the action of our fingers), shoes (which strengthen the action and resistance of the feet), clothes in general (which enhance the protective action of the skin and hair), and ladles and spoons (which substitute for and improve the action of the hand seeking to collect a liquid and bring it to the mouth).
Another device that might be considered an extensive prosthesis is the lever, which in principle works like the arm but better; but the lever does this so well, and with such results, that it probably ushers in a third category, that of magnifying prostheses. These do something that our body had perhaps dreamed of doing but without ever succeeding: telescopes and microscopes, but also vases and bottles, baskets and bags, the spindle, and certainly the sledge and the wheel.
Both extensive and magnifying prostheses can also be specified as intrusive. Among the extensive-intrusive prostheses, we would mention the periscope or certain medical instruments that make it possible to explore immediately accessible cavities such as the ear or throat, while the magnifying-intrusive prostheses include scanners, gamma-ray measuring devices in nuclear medicine, or certain probes equipped with miniature television cameras that explore the entire intestines and project what they «see» onto a screen.21
I have made use of this attempt at classification only to be able to talk of that original and special type of prosthesis, which is the mirror.
6.11 More on Mirrors22
What is a mirror, in the current sense of the term? It is a regular plane or curved surface capable of reflecting rays of incident light. A plane mirror forms a virtual, upright, reversed (or symmetrical), specular (of the same size as the object reflected) image devoid of so-called chromatic aberration. A convex mirror forms virtual, upright, reversed, and reduced images. A concave mirror is a surface of a type that (a) when the object is between the focus and the spectator, it forms virtual, upright, reversed, enlarged images; (b) when the object’s position varies, from infinity to coincidence with the focal point, it forms images that are real, reversed, enlarged, or reduced, depending on circumstances, at different points in space, which can be observed by the human eye and collected on a screen. Paraboloidal, ellipsoidal, spherical, or cylindrical mirrors are not in common use and, if anything, are used for deforming images and in catoptric theaters.23
In Eco (1985) I was struck by the oddity and the quasi «idealistic» nature of the idea—established in optical studies—that the mirror image is reversed or, rather, «inversely symmetrical.» The naive opinion that the mirror puts the right in place of the left and vice versa is so deeply rooted that some people are surprised by the notion that mirrors reverse left to right but not up to down. Now let’s reason for a moment: if in front of the mirror I have the impression that it reverses right and left, because in the image it seems that my watch is on my right wrist, for the same reason, if I look into a mirror on the ceiling, I ought to think that it has changed up to down, because I see my head where my feet ought to be.
But the point is that not even vertical mirrors reverse things or turn them upside down. If we make a diagram of the specular phenomenon, we realize that camera oscura—type phenomena do not occur in it (see fig. 6.5): there are no intersecting rays in specular reflection (see fig. 6.6).
Figures 6.5 and 6.6
The mirror reflects our right exactly where our right is, and the same holds for the left. It is we who identify ourselves with the person we see in the mirror, or think that it is another person standing in front of us, and we are surprised at his wearing a watch on the right wrist (or his gripping a sword with the left hand). But we are not that virtual person in the mirror. All we have to do is avoid «entering» the mirror, and this illusion will no longer trouble us. In fact, we can all manage to comb our hair in the mirror in the morning without acting as if we had cerebral palsy. We know how to use the mirror, and we know that the lock of hair over our right ear is on our right (even though for the person in the mirror, were he there, it would be on the left). On the perceptual and motor plane, we correctly interpret the mirror image for what it is, but on the plane of conceptual reflection we still cannot entirely manage to separate the physical phenomenon from the illusions it encourages, in a sort of hiatus between perception and judgment.
We use the mirror image the right way, but we talk about it the wrong way (whereas in astronomy we talk correctly about the relation between the Earth and the Sun, even though we perceive it wrongly, as if it were the Sun that moved).
This is certainly a very curious point: that mirrors reverse left and right is an ancient belief, from Lucretius to Kant, and some cling to it to this day.24 If things were like this, we would have to think about the fact that, when
