Malebranche and occasionalism
The action of the body on the mind and of the mind on the body is impossible; consequently, it is God who acts alone, conforming the will of the mind to the acts of the body.
Leibniz and the pre-established harmony
Gottfried Wilhelm Leibniz posits that the universe consists of monads that are closed to the outside world. So how do you explain that everything happens in the world as if the monads really influenced each other? Leibniz explains this concordance by a universal preestablished harmony between all beings, and by a common creator of this harmony:
“Thus God alone makes the connection and the communication of substances, and it is through him that the phenomena of some meet and agree with those of others, and consequently that there is reality in our perceptions.“ (Speech on Metaphysics)
If the monads seem to consider each other, it is because God created them to be so. It is from God that monads are created at once by fulguration, in the state of individuality that makes them like little gods. Each has a view of the world, a view of the universe in miniature, and all its perspectives together have an internal coherence, while God has the infinite points of view he creates in the form of these substances. individual. The intimate strength and thought of the monads are therefore a divine force and thought. And harmony is from the beginning in the spirit of God, i.e. it is pre-established.
Harmony being pre-established, it has a happy consequence:
Since there are two kinds of truths: “There are also two kinds of truths, Reasoning and Faith. The truths of Reasoning are necessary and their opposite is impossible, and those of Faith are contingent and their opposite is possible. When a truth is necessary, reason can be found by analysis, resolving it into simpler ideas and truths, until we come to the primitives “(Monadology, paragraph 33), and “However, we must not imagine with some, that the eternal truths, being dependent on God, are arbitrary and depend on his will, as Descartes seems to have taken and then M. Poiret. This is true only of contingent truths, the principle of which is convenience or the choice of the best; instead that the necessary truths depend solely on his understanding, and are the internal object of it.“(Monadology, paragraph 46), so science can then dispense with deciphering the divine will to understand the world, it is enough to understand its understanding , defined as rational.
The dualism of psychoanalysis
More or less derived from philosophy, the “dualism” of psychoanalysis is one of the pillars of Freud’s metapsychology, and is accepted by most of his heirs. However, this dualism is a dualism of the drives and it is rather artificial to suppose between this drive dualism and the “substantial” dualism other than a distant relation of analogy. Without using the term “dualism” Freud has always built his clinic and his theories on the idea of a dynamic conflict between impulses, first between sexual impulses and urges for self-preservation, and later between “impulses” of life and death. Before him, Gustav Fechner and others had attempted to account for the link between body and mind by psychophysics. In contrast Carl Gustav Jung and Pierre Janet are presented as monists. Neuroscience also postulates a mind-body unity, a monism; referring in particular to the opposition Spinoza – Descartes.
Objections against dualism
There are at least three classic apories for dualism; these objections were developed, inter alia, by Baruch Spinoza and Daniel Dennett:
- the problem of the interaction between body and mind; the relation of two causalities of different natures is unintelligible. Indeed, the alternative seems to be the following: either the body and the mind are in a relation of causality, and in this case they are of the same nature, so there is no dualism (but the problem of their reports is not resolved); or, not being of the same nature, they each have their own causality.
- solipsism: to understand this objection, it is possible to start from an experience of thought invented by Descartes (Meditations on First Philosophy): looking in the street through the window, I see “hats and clothes” that move; how can I know that they are not machines that make them move, rather than men like me? The problem of dualism is that in this “thought experiment”, the only knowledge of spiritual reality is that which everyone has in a “private” sphere that is called “interiority”; it follows that I can attribute a spirit to others only to the extent that what appears “publicly” from him conforms to an intelligible conduct to which I can relate motives, decisions, etc., which are peculiar to me. So I do not know with any certainty whether someone else is also a spirit, besides being the body I see. The mind, according to this hypothesis, seems to become what has been called a ghost in the machine (Ryle).
- the problem of self-knowledge and private language. According to dualism, every man has an “interiority”, that is, a private “intimate forum” in which he perceives himself feeling and thinking. In this hypothesis, everyone knows each other intimately, and it is impossible to be mistaken about one’s own thoughts and perceptions. Now this thesis, which in Western culture has gradually become an “obviousness” for almost everyone, poses serious difficulties. These difficulties were particularly raised by Nietzsche, then in the framework of analytic philosophy, by Wittgenstein. The first of these difficulties is that we seem to know of the “me” only generalities that express themselves through a public language. But our interiority is, at best, a “flow of sensations” that we can not express in themselves. Thus, when we designate the red color that we feel, we speak of red in general – of the notion – and never of this red which is not red, but a sensation of which we say publicly that it must “correspond” to the notion “red”. This entails several difficulties: such a declaration, on our inner life, is “unverifiable”; but it is also incomparable, to the point that, perhaps, we will not be able to reach any intersubjective agreement on the identification of such a “sensation”. These difficulties then affect, among others, the question of “the foundation of science”: if one wants, like Carnap, to base the scientific observation on a “private” language, on an “individual” protocol which can be used to establish the fundamentalist thesis of science, this protocol escapes, in the end, any “objective” investigation. Henceforth, science has no ultimate foundation, but is constructed only from pre-existing theories.
All these objections, designated by Ryle by the expression of received doctrine, leads to consider the problem in an exclusively monistic perspective (reductionist or not): either materialism or idealism.