Bishop George Berkeley
 

1. We only know our mind and ideas.
   Primary and secondary qualities are subjective.

Arguments:

   If a quality is relative, then it is subjective.
   Primary and secondary qualities are relative.
   Primary and secondary qualities are subjective.
 

   Primary qualities cannot exist apart from secondary qualities.
   Secondary qualities cannot exist apart from a mind.
   Primary qualities cannot exist apart from a mind.

2. Mental substance supports primary and secondary qualities.
   Ideas depend on perceiving minds for their existence.

3. We do not know abstract concepts. (nominalism)
   A concept is an picture in the mind.
   We can only picture particular things.
   Abstract concepts stands for groups of similar particular things.
   Matter (material substance) is an abstract meaningless concept.
   Matter does not exist.
   The idea of a thing that is not an idea is unimaginable.

4. To be is to be perceived, or to perceive. ("Esse est percipi")
   This leads to solipsism - only the self exists.
   People believe their cars and houses exist unperceived.
   These are objects of the senses.
   It's a contradiction to think that sensations exist unperceived.
   Note:
   We are saying the cause of sensations exists unperceived.
   We are not saying that the sensations exist unperceived.

5. Material objects are bundles of sensations/ideas.
   Subjective Idealism
   Occam's Razor
   Naive Realism - Things exist exactly as we perceive them.

   Berkeley's Problem:

a). All we perceive are ideas.
        b). We know the existences of physical objects.
        c). Physical objects are not ideas.

   Berkeley's Solution:
        c). Physical objects are bundles of sensations.

 Arguments:

   Task - Conceive of anything existing unperceived.
 

   Physical things are sensations.
   Sensations depend on a mind;
   Therefore, physical things depend on a mind.

   Physical objects are objects of knowledge.
   Objects of knowledge are ideas.
   Ideas are mental and in the mind.
   Therefore, physical objects are mental and in the mind.

6. God perceives reality.

   Sensible things don't depend on human minds.
   To be is to be perceived.
   God must perceive them.

   Berkeley is a subjective idealist:
   There are individual minds and the external mind of God.
   Objective idealism: everything is the mind of God.
   Omniscience is the basic nature of reality.
   Solution to the problem of evil.