We leave Siris's disjointed text with little sense of the whole and no impression of any central tenet around which it was organized. No ‘esse is percipi’ looms large in our memories. Siris presents such a variety of doctrines on so many subjects, and all in such a tentative fashion, that any clear perception of what the book was about is denied us. Instead Siris encourages us to participate in a mode of inquiry. Its form and style ask us to join Berkeley in his reflections, and under his subtle direction we come to experience a technique of interpreting the natural world.

It is surprising to discover Berkeley investigating natural causes in Siris, let alone teaching a method of ‘philosophical’ inquiry. Much of his career was devoted to attacking modern natural philosophy on the grounds that it detracted from the more central and valuable sciences of theology, ethics and metaphysics. Berkeley's most thorough criticism of the method of contemporary science came in De Motu, a tract written in 1720 for a competition organized by the French Academy. There he warns physicists to be less dogmatic in attributing occult qualities to objects and more faithful to sensible evidence. Above all he insists they renounce their claims to identify causes in nature, a task which belongs to the metaphysician alone. He thus demotes the scientist to the position of nature's cataloguer, one permitted only to observe the regularities in natural phenomena and from these determine ‘apparent’, but not true causes and laws. In De Motu Berkeley's underlying philosophy of science is instrumentalist: scientific explanations are never perfect, but are only proposed as the best interpretations available.