One of the important aspects of philosophy is that it can question the truth of our fundamental beliefs that the vast majority accept without doubt. Among the most important of such beliefs is about objects outside of us, such as a table, trees, animals, stars, etc., or about the existence of the world as a whole. We believe, at least for practical purposes, that those objects exist and that they have certain properties: for example, the ball is round, the tree’s leaves are green, etc. However, there are also ideas in philosophy that question whether objects really have the qualities we believe they possess or whether there is a world outside us. Such ideas are found in the writings of philosophers like Sextus Empiricus, Michel de Montaigne, Augustine, Descartes and Hume. In this article, we will look at several corresponding arguments of skepticism in general.
When we carefully observe the various objects that we often see in our daily life, it becomes clear that we can often be mistaken about them. For example, imagine you are looking at a cabinet in your room. And looking at it, you believe that it’s brown and has the shape of a rectangular parallelepiped. At first glance, this belief seems undeniably true to many of us; most other people who saw this cabinet would confirm the truth of this belief. But if you take a closer look at your cabinet, you will see that its surface is not monotonous in color; some parts of its surface are brighter or perhaps whitish than others, depending on the incidence of light. If you move slightly to the right or left of where you are standing in front of the cabinet, or if the direction of the light falling on the surface of the cabinet has changed, parts that appear bright and whitish will become darker, while some other dark parts will appear bright and whitish. Therefore, the color of the said cabinet depends on the lighting of the room and our viewing position in space. In addition, colorblind people or people wearing colored glasses will see the cabinet as a completely different color. When the room is dark, it will appear darker. If we summarize what has been said, we can say that even if at first glance we think that the cabinet is the same color, in fact, it appears in different colors from different viewing angles; that is, the position of the subject who sees color in space changes depending on the characteristics of her perceptual apparatus and the lighting. Thus, it can be concluded that our belief that the cabinet in the bedroom is brown is problematic because its color changes depending on the subjective factors; it is not consistently brown. It would be wrong to believe that the color, which changes depending on the subject’s perception, is a real property of the thing. Therefore, we cannot consider the color of the cabinet that is manifested to us as real, i.e. an entity having an existence independent of our mind. [i]
Similar conclusions would apply to the shape of the cabinet. Because the shape of the cabinet that we see does not remain constant like its color—it depends on different viewing angles—the cabinet appears to observers in different forms. The front of the cabinet, which is considered to have a rectangular shape, appears to have two acute and two blind angles from almost all different viewing perspectives, and if we change our position in space, the originally acute angles will appear as blind angles, and the originally blind angles will appear as acute angles.
True, we do not usually pay attention to such changes in color and shape based on our different viewing positions. Despite these perspective-dependent changes, our perceptual system immediately produces what we perceive to be “real” colors and shapes from color and shape appearances, and thus, we persist in believing that the cabinet remains the same color and shape despite our mutable senses. However, when we reflect on sense-data presented to our perceptual apparatus, it becomes clear that, as in the color example, even if we think that the cabinet has a fixed shape, in fact, its shape changes depending on the position of the subject in space and the characteristics of the perceptual apparatus. And if the cabinet has a real shape, given that the shape has remained unchanged during this time, then it turns out that what our senses present to us is not the real shape. In other words, there is room to doubt the truth of our belief that the cabinet in our bedroom has the shape of a rectangular parallelepiped, at least because our senses do not present it to us as a fixed rectangular parallelepiped.
In this respect, a similar situation exists for other kinds of senses. When we touch the cabinet, it gives us a feeling of solidity, but this feeling we experience varies depending on how much pressure we apply to it and to which part of our body we apply pressure. Or the sound produced when knocking on the cabinet again depends on the intensity and pressure with which we knock, as well as subjective factors such as the structure of our ear and the distance between it and the sound source.
Thus, the conclusion reached on the basis of the foregoing is that even if the cabinet exists independently of our perception (i.e., is real), we do not have direct access to its properties (color, shape, solidity, etc.). We can at best assume that there is an object (the “cabinet” of our example) behind the color, shape, sound, etc. appearances; and even if we do not have direct access to that object, as well as its properties, it is that object or its properties that cause said appearances. But in this case, we must accept that we cannot have definite knowledge about what the object is like in itself, whether its properties correspond to the appearances observed by our perceptual apparatus or not.
In this context, it is possible to take a more pessimistic view of the existence of external objects because we can only assume that there is an object behind the appearances, without being certain of its existence. However, it is also possible that there is nothing real or objective behind these appearances. That is, we have no way of knowing at all whether there is a reality outside of our mind.
In addition to questioning the ability of our senses to inform us about the world as it is, the main arguments motivating such a radical position, skepticism, have to do with illusions,[ii] hallucinations, and dreams that are perceived as reality. Occasional occurrences of hallucinations, that is, when something appears to the eye without any relevant external object, as well as in some cases the inability to distinguish sleep from waking, strengthen the doubt that what is perceptually manifested to us corresponds to reality in general. This is because we have no way to check whether what is manifested to us is a hallucination or a long dream, and because it is logically possible that what we experience at any given moment is a dream or a hallucination. The frequent occurrence of deceptive dreams, illusions, and hallucinations indicates that our senses can mislead us. And since our senses can mislead us, we cannot be sure that they do not mislead us in other cases.
Thus, according to such skeptics of the external world, as long as we live a conscious life, we cannot be sure that perceptual appearances actually correspond to real objects. Even if there is a world outside us, since our direct access to it is possible by way of sensory and perceptual mediation, the beliefs we form about the external world have no solid basis. And as long as there is no solid basis, then there is a reason to doubt the existence of the world outside us in the way it appears to us, as well as its existence in general. This is the argument of skepticism.
We will try to look at the opposite positions in our forthcoming articles.
Notes and references
[i] In fact, when thinking about color, two different concepts of color may come to mind. First, under the influence of physics, we can say that color is the property of objects to reflect light waves, that is, it exists independently of mind. Secondly, color can be described as a subjective property, which is a property of an object that appears to a normal observer under normal conditions. Here we are talking about the latter concept of color.
[ii] Illusions are encountered by every person with normal perception from time to time, if not daily. For example, when most of us are driving in hot weather, when we look at the asphalt, it seems to us that it is moving or as if it is evaporating (mirage). Another example: the right and left parts of a railway line seem to meet at a distance, but no matter how much you travel along those railway lines, you will never reach their meeting point, because there is no such point. However, the lines will still appear to converge at a distance. Another classic example: a stick partly immersed in water appears to be bent at the water’s surface.
