+

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.