George Berkeley was the first of the major idealists. The philosophical doctrine he is most famous for is the rejection of the motion of material substance. Berkeley argued all we have is experience. In this position he was arguing against Locke. It should be stated that Berkeley was not a skeptic, though he rejected the notion of material substance.
He didn't doubt and yet he proposed that the whole of reality is spiritual. He advanced what was largely a theological perspective.
Locke had turned the material world into a "god" in the opinion of Berkeley. Nature had come to be regarded as possessing a nature of its own and consequently God was no longer needed. This is seen in the perspective of the deists in which God creates what exists and sort of "goes on a holiday" leaving the created order to work for itself in his absence.
Berkeley views this as atheistic. He proposed that matter should not e given equal status with the spirit and in this sense Berkeley was one of the first to have the idea of turning the tables by making the sensible world to be nothing in essence and also regarding what we believe is the material world to be wholly mind dependent.
Berkeley asserted only that there is the world as it appears to be in contradistinction to Locke who allowed that there is actually a world out there for us to experience.
However, Berkeley granted legitimately to science. One would expect Berkeley to do otherwise due to his dismissal of the existence of the material world. He proposed an analogical explanation.
Suppose I see a fire and I know the fire will burn me. Unless the ideas that God instills within us were in some sense orderly, they would be useless to us. We could sum up this belief by concluding that we are on the one hand infinite sprits and on the other hand infinite spirit and yet we are all somehow in communication with God via our experience. All of the regularity in the world we know thru science is the grammar and syntax of God's language.
In short, for Berkeley all reality is mental.
