Descartes regarded matter as inert, passive extension. Both Descartes and Locke considered that our ideas of sensible properties (such as colors, tastes, smells) did not really inhere in or belong to the physical world, but rather were effect produced in the mind alone. Reflection on these issues and distinction led the Irish philosopher George Berkeley to the radical conclusion that nothing at all could be said to exist outside the mind.
Berkeley's immaterialism has often been regarded as an affront to common sense. Berkeley however refers to houses, mountains, and rivers, and to all those bodies, which compose the frame of the world. He does not deny the reality of such things but asserts that their existence consists in their being perceived. Berkeley put it in Latin, their esse est percipi or "to be is to be perceived."
So the consequent question emerges from Berkeley's Metaphysical conclusion, "Does the table in my study continue to exist when there is no one in the room?" Berkeley suggests at one point that to say it does, means that "if" I were in my study I would perceive it (a view sometimes called "Phenomenalism"). But Berkeley more characteristically advocated that tables, chairs, mountains, rivers and all natural phenomena do indeed have a being independent of the human perceiver. They exist in the "mind of some Eternal Spirit". God, therefore, is the divine perceiver.
The following has been offered as a response to, and a response on behalf of, Berkeley's conclusions:
There was a young man who said,
"God must think it exceedingly odd.
If he finds that this tree
Continues to be
When there's no one about in the Quad."
Reply:
“Dear Sir:
Your astonishment's odd:
I am always about in the Quad,
And that's why the tree
Will continue to be,
Since observed by
Yours faithfully,
God.”
Berkeley offers a picture of reality as something essentially mind-dependent, and grounded in the divine consciousness.
