  Implicit in the answer above is Berkeley’s insightful account of scientific explanation and the aims of science. A bit of background is needed here to see why this issue posed a special challenge for Berkeley. One traditional understanding of science, derived from Aristotle, held that it aims at identifying the causes of things. Modern natural philosophers such as Descartes narrowed science’s domain to efficient causes and thus held that science should reveal the efficient causes of natural things, processes, and  events.[16]   Berkeley considers this as the source of an objection at Principles 51: