Berkeley’s perceiver

Berkeley argued that the things we perceive are collections of ideas, and that nothing perceived exists apart from a mind. His formula is esse est percipi, to be is to be perceived (Principles, §3, along with the spirit that perceives it). In §6 he says the whole furniture of the world has no existence outside a mind. He meant this as a defence of common sense against the philosophers’ unperceivable matter. A table is real because I see and feel it.

The obvious objection is the table in the empty room. Berkeley first replies that if he left the room, the table would still exist in this sense: he, or some other spirit, would perceive it if he were there (§3). The harder question is whether things stop existing whenever nobody perceives them. That’s where the argument got famous. In the Three Dialogues he says ideas of sense exist in an infinite mind. So things carry on when no finite mind perceives them, because God does.

Commentators don’t agree that this is secure. The SEP notes that sensory ideas can’t be copies of God’s non-sensory ideas, and that God’s ideas would cover objects we wouldn’t call real. One proposed fix ties continued existence to God’s decrees to produce the ideas. Then the world exists as a lawful pattern of what would be perceived.

In sandbox terms, this is a rendering policy. With Observation set low, only what’s being perceived gets computed. Berkeley’s world is the policy where nothing is ever unobserved, because a standing observer keeps every state. His theology does the job that unlimited computing power would do.

The comparison cuts both ways. A computed world doesn’t need a divine perceiver. It needs a store of state and a rule for producing a view of it. A developer who stores state has a fact about the unobserved table. Berkeley wanted the opposite. For him, there’s no fact beyond ideas and what would be perceived.