Gottfried Wilhelm Leibniz, Existence, Necessity, and Gottfried Wilhelm Leibniz, Existence, Necessity,

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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




    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

  • +

    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


    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.