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Gottfried Wilhelm Leibniz, Existence, Necessity, and God
Discourse on Metaphysics The Monadology
+The Ontological Argument Fifth Meditation The Monadology
+Knowing the essence of an octagon
n “All octagons are red.”
n not universal or eternal
n contingent
n fallible
n “All octagons have interior angles that sum to 1080 degrees.”
n universal and eternal
n necessary
n certain
+Necessity and possibility
n p is necessarily true = not-p is impossible n necessary beings
n p is contingently true = p is actually true, but not-p is possible n contingent beings
n Examples of... n contingent truths?
n necessary truths?
n possibilities that are not actual?
n What is a possible world?
+The Ontological Argument
1. If my (clear and distinct) idea of X contains some property, then that property belongs to the essence of X.
2. My idea of God contains every perfection. n Perfection: positive trait or property
3. Existence is a perfection. n Existence is more perfect than non-existence.
4. Therefore, existence belongs to God’s essence.
5. Therefore, God necessarily exists.
6. Therefore, God actually exists.
Descartes’ version
+The Ontological Argument
1. My idea of God contains every perfection.
2. Necessary existence is a perfection.
3. If my idea of X contains a property, then it is impossible for X to exist without having that property.
4. Therefore, it is impossible for God to exist contingently. (1-3)
5. It is possible for God to exist.
6. Therefore, God necessarily exists. (4 and 5)
7. Therefore, God actually exists.
Leibniz’s version
+Mind-Body Parallelism Discourse on Metaphysics The Monadology
+Mind-body interactionism
Decision to kick
kicking
pain
“ouch!”
n Mental events cause physical events:
n decision to kick causes foot to kick the wall
n sensation of pain causes utterance of “ouch!”
n Physical events cause mental events:
n foot kicking the wall causes sensation of pain
+Interaction problem
n Tension in Descartes: n Bodies interact by
touching… n …but mind has no extension
or location.
n Newton: Bodies can interact at a distance… n …but it’s still depends on
mass and location.
n Q: What is the First Law of Thermodynamics?
Princess Elisabeth of Bohemia
+Mind-body parallelism
n Parallelism: mind and body do not interact
n correlation between mind and body without causation
Decision to kick pain
kicking “ouch!”
n Leibniz: all substances like synchronized clocks
n Who synchronized them?
+Monads The Monadology Discourse on Metaphysics
+What is a continuum?
n It’s complicated.
n Two important features:
n Densely ordered—between any two points there’s another
n Totally ordered—every number is related to every other
n Comparison with space:
n divisibility of everything which is spatially extended
n spatial relatedness of all material bodies
+Descartes vs. the atomists
n Democritus: “By convention there is sweetness, by convention bitterness, by convention color, in reality only atoms and the void.” n Conventional?
n Descartes added ‘hardness’ to the list.
n Arguments against atomism: n If atoms are extended, then they
are divisible. n You can’t imagine two atoms in the
void without appealing to secondary qualities.
Democritus of Abdera
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Monads: “the true atoms of nature” mind-like, not spatially extended
causally isolated
building blocks of all matter
Are you a monad?
+Monads: mirrors of the universe
n Monads are causally isolated, but space is a continuum.
n How is an isolated monad related to the rest of the universe? n perception: something in you that reflects another
substance
n Spatial relations are reducible to perceptions contained in individual monads.
n Leibnizian idealism: physical properties reducible to mental properties
+Summary
n Monads: indivisible substances, each of which reflects, in its own inner nature or essence, the rest of the monads in existence
n Problem of evil: God selected the best possible collection of monads, whose essences are in harmony with one another.
n Free will: Your actions are free because they come from your own essence. “Laws of nature” are due to the harmony between the monads God selected.
n Composition of the Continuum: Our ideas of space correspond imperfectly to the coordinated essences of spatially unextended monads.