The dichotomy between external and internal originates from the dualism of two substances presented by René Descartes. The dichotomy can be done in two ways. One is open Cartesian dualism of two substances: the material substance with three spatial dimensions and the immaterial substance of reason with only one dimension, time. The other one is called crypto-Cartesian dualism: What René Descartes said about the soul, is said about the brain [1, 111–114]. The brain thinks, wills, decides, and contains experiences, perceptions, thoughts, qualia, and so on. In both cases the essential feature of the dichotomy is that mental processes and contents are separated from the external world of facts.
Cartesian dualism created the epistemological problem of how an immaterial consciousness can acquire knowledge about the external material world, about the hidden causes of perception. Baruch Spinoza already pointed out to Cartesians that if the two substances, material and immaterial, have no common attributes, then there cannot be any reasonable explication of their connection. It is fairly safe to say that Spinoza got it right. However, the tricky epistemological problem is still with us.
Crypto-Cartesians are committed to explain how mental states and processes can literally reside in the brain. According to David Chalmers a qualitative feel, a quale, really is internal . A look at a red rose produces an internal quale of redness that is entirely subjective. But what are colours? In normal circumstances there is a source of light, a reflecting surface containing pigment that reflects some wavelengths of light and absorbs others, and eyes with retinal cells that also contain pigment. The pigment in the retinal cells functions in the same way as the pigment in the reflecting surface: some wavelengths are reflected away and some are absorbed. In the cells the electro-magnetic energy of photons is transformed into electro-chemical energy, neural impulses. These impulses are not coloured. The point is that the interplay of light, reflecting surface and retinal cells is a necessary condition of colour perception (not sufficient condition as other parts of the central nervous system participate in the process). This interplay, an aspect of organism environment interaction, just cannot be transferred literally in the brain. It is quite inconceivable how a red flash might emerge in the dark brain. By virtue of what would some neural activity in the brain qualify as a red quale? This remains an open question.
John Searle is, however, quite persistent. “These states, qualia, are entirely caused by brain processes. We are not quite sure what the causal mechanisms are, but neural firings at synapses seem to play an especially important functional role” [22, 99]. Unfortunately Searle has nothing constructive or illuminating to say about what these causal mechanisms might be. Of course, some day someone may find out, but instead of waiting for this we might consider an alternative. The dichotomy between external and internal can be rejected as a speculative metaphysical conjecture that has no solid empirical evidence to support it and only creates artificial problems, which are best solved by dissolving them, by showing that these questions are not worth asking. This can be done by presenting a credible alternative.
The dichotomy between external and internal is present also in the discussion about the core features of rational thought, namely the classical laws of thought: the principles of contradiction and excluded middle. Leila Haaparanta appeals to Edmund Husserl and claims philosophical naturalism, which holds that all knowledge is based on experience, is an impossible doctrine because it leads to contradictions and absurdities [10, 99]. According to Husserl naturalism does not acknowledge the ideal realm as “eternal, self-identical, timeless, spaceless, unmovable and unchangeable” [9, 156]. This is the realm of basic forms of thought, which cannot be naturalized. The basic logical concepts and laws “draw the limits of thinkability” [10, 37]. “We may assume that a first logic or the primary epistemic structures are present and they are presupposed in all knowing, but we are quiet about them, because every effort to say something about them would lead to absurdities” [10, 45].
However, the description of how the principles of contradiction and excluded middle were invented is not a bit absurd. Aristotle developed his doctrine of syllogisms as a method of analyzing the validity of a syllogism on the ground of the formal features alone. Aristotle rejected the Platonic dualism of empirical objects and the ideas or forms of them. Objects can be perceived but forms can only be thought of. Aristotle dragged the Platonic forms down to earth as the essences of empirical objects. The objects can be classified unambiguously. The essence determines the class to which objects belong. Every object belongs to one and only one class by virtue of its essence. No consider the following syllogism:
Animals are mortal.
Horses are animals.
Ergo: Horses are mortal.
How do we discover the form of the syllogism? In a very simple way: by taking off the content, namely the talk about animals, horses and mortality. In the first sentence there is the class of animals, and in the second sentence there is its subclass, the class of horses. We can drop the talk about animals and horses if we maintain the formal feature, namely the fact the class mentioned in the second sentence is a subclass of the class mentioned in the first sentence. Further, we can drop the talk about mortality if a formal condition is fulfilled, namely the fact that the property under discussion is an essential property of the upper class. All the essential features of the upper class are essential features of all its subclasses. All syllogisms with these formal features are valid.
Now how about the above mentioned laws of thought? The law of the excluded middle says that everything is either A or not-A. Aristotle presumed that the objects in the world are exhaustively classified. Every object belongs to only one class. This law is a generalization of this presumed feature of the world. Any object under examination is either a horse or a cow or a zebra or a rose, and so on. Instead of a long list we can say simply horse or not-horse. The statement that this is a horse is either true or false. Similarly essential features either do or do not belong to an object. Claims about them are either true or false. Animals are not only partly mortal. The law of contradiction says that A is not not-A. That is, if the object under examination is a horse, then it cannot belong to any other class. Horse is not not-horse. Similarly statements about essential features cannot be true and false at the same time.
All this is based on what Aristotle presumed the world to be like. The formal structure of thinking with syllogism is derived from the structure of the world as it is divided to classes of objects on the ground of their essential features. The presumptions of Aristotle about the world are wrong, but it is not the point. This is anyway the origin of the laws of thought. Later on, with the favourable assistance of René Descartes, these laws were lifted up to the heaven as supernatural features of human mind beyond the scope of rational discussion. What part of this story is absurd?
The alternative provided by classical pragmatism is to admit that we are embodied beings living within nature. The focus should be on organism environment interaction, on the practical orientation to the world. To know is to know what to do. The object of knowledge does not consist of the hidden causes of perceptions. The proper object of knowledge is the relation between two situations, a problematic situation and a later situation where the problem is solved. In the problematic situation one has to identify the problem, find out what information is needed for solving it, use any available method to get that information, and formulate a hypothesis of what to do, what operations might lead to a situation where the problem is solved. If this is successful, then we have knowledge that is valid enough (for time being, new problems tend to emerge). . There obviously are hidden things in nature. The history of science shows that new phenomena are discovered every now and then, but there is no need to take them as objects of knowledge before there are some means (like experiments and measurements with various instruments and devices) to get them within our empirical access to the world.