God \ Mind \ Matter: For Descartes, extension is the essence of matter; for Spinoza, only God alone; Leibniz rejected extension as the attribute of substance, and a denial of the reality of matter
The conception of Substance: derived from subject and predicate. Some words can be either subjects or predicates; others can only occur as subjects -- these words are held to designate substances.
Descartes
- Principia Philosophaie 1644 -- regarded the bodies of men and animals as machines; animals he regarded as devoid of consciousness; men have a soul which comes into contact with 'vital spirits', and though the soul cannot affect the quantity of motion in the universe, it can alter the direction of motion. 'My arm moves when I will that it shall move, but my will is a mental phenomenon and the motion of my arm a physical phenomenon. Why...does my body behave as if my mind controlled it? ...Suppose you have two clocks: whenever one points to the other hour, the other will strike, so that if you saw one and heard the other, you would think the one caused the other to strike'
- the idea was that the soul was in a sense, wholly independent of the body.**This theory explained the appearance of interaction while denying its reality. The first law of motion - a body left to itself will move with constant velocity in a straight line, but there is no action thereafter. All interaction if of the nature of impact.
- Discourse on Method 1637, Meditation 1642 -- 'I think therefore I am'. I may have no body or be deceived by my surroundings, but nothing could deceive me if I did not exist. I am a thing that thinks. The process by which this argument is reached is called 'Cartesian doubt'. The qualities of an object can change, but the essence of the object, can still be understood by the mind, hence the conclusion that the perception of external things is acquired by the mind, and not the senses.
Spinoza
-Ethics -- sets forth an ethic baed on metaphysics and the psychology of the will
- God \ Mind \ Matter -- mind and matter were independent substances, but were both attributes of God. There is no free will as everything that happens is a manifestation of God's nature. The mind has knowledge of the eternal and infinite essence of God but the passions distract and obscure our intellectual vision of the whole. Passions are governed by self-preservation until we realize that what is real and positive is what unites us to the whole. When man grasps the sole reality of the whole, he is free. 'The mind can bring it about, that all bodily modifications or images of things may be referred to the idea of God'. There is something in the human mind that is eternal, and in God an idea which expresses the essence of this, and this idea is the eternal part of the mind.
- It is important to distinguish Spinoza's ethics from his metaphysics. His metaphysic can be called 'logical monism' - that the world as a whole is a single substance, and the belief that every proposition has a single subject and predicate, which leads us to the conclusion that relations and plurality is illusory.
- In his ethics, he shows how it is possible to live nobly even when we realize the limits of human power - e.g. 'nothing that a man can do will make him immortal, and it is therefore futile to spend time in fears and lamentations over the fact that we must die'
Leibniz
- extension involves plurality and therefore belongs to an aggregate of substances; an infinite number of substances, which he called 'monads' . Monads form a hierarchy, in which some are superior to others in the clearness and distinctness which they mirror the universe; a human body is composed of monads, but there is one dominant monad, the soul.
- Arguments for the existence of God:
1) in the case of God, essence implies existence, because it is better that a Being who possesses all perfection exists that not, and a perfection is defined as a quality which is positive and absolute
2) refers back to Aristotle's argument of the unmoved mover. Everything finite has a cause, which in turn had a cause, and so on. But the first term must not be uncaused, and that is God. Kant - if the existence of the world can only be accounted for by the existence of a necessary Being, then there must be a Being whose essence involves existence. And if so, then reason alone, without experience, can define such a Being. There must be a reason for this contingent world, and this reason must be sought among eternal truths; hence a reason for existence must exist, and can only exist as eternal truths as thoughts in the mind of God, the single cause that regulated the minds.
