Proofs of the External World

Physical Objects

• Doesn’t rely on our experience

• We see physical things through vision, but judge that it’s present through understanding

• Understanding of the concept of physical objects is a priori

Wax Analogy

• If you melt a piece of wax it loses all primary qualities

• We can’t think of the wax as it’s sensory qualities

• I can image the wax can undergo more changes, like changes in extention

• My concept of the wax as extended and changeable cannot come from my perceptual experience

  • I know it has the capability of changing extension, even if I’ve never seen it change

I perceive the wax by my mind alone.

Only the thought of the wax is clear and distinct - not the actual experience.

We see physical things through vision, but judge that it’s present through understanding → a priori

External World

• Our sensations are not subject to our will and are uncontrollable

  • Ex. can’t choose what to hear

• Our will is part of us as thinking things

  • Our sensations don’t come from within but from a different power

• Our sensations are extended - representing things with size & shape

• Our minds are unextended

  • Spatial things can’t come from an un-spatial thing

  • It must come from something external

God Is No Deceiver

• Either sensations must come from the material world or God

• He already has a strong inclination that the physical world exists

• God wouldn’t allow him to believe that, if it were false

  • God is omnibenevolent and no deceiver

• His sensations must originate from material objects

Proof

• We all have a clear and distinct idea of objects as extended and changeable

• We tend to think that objects exist

• We already know God is no deceiver so guarantees the truth of my clear & distinct ideas

• We know that the external world exists

Criticism

Concept of extension is from Sense Experience

• It is not clear and distinct

• It’s derived from sense experience & abstraction of our changeable experiences

Berkeley - Mind-Independent Substance

• We dont experience mind independent SUBSTANCE

  • All qualities are experienced mind-dependently

• Experience doesn’t support the existence of substance

  • Surely it’s confused and not real outside the mind

Descartes hasn’t proved that physical objects exist mind-independent

Empiricists - Best Hypothesis Russell

• The external world is imply the best hypothesis of my perception

• It explains the coherency and involuntary nature of my perceptions

• This doesn’t mean it’s certain but is supported by Okam’s Razor

Hume - Confusion of Simularity & Identity

• Because a table looks the same each time we see it, we assume it’s the same table

• Therefore we mistakenly derive the concept of a physical object

• Goes against Locke, Russell & Descartes

Evaluation