 Thirdly, according to Boyle, once a theory is constructed, the natural philosopher should be prepared to revise it in the light of new experimental evidence: “I would have such kind of superstructures look’d upon only as temporary ones …” (BW, 2:14). The only things that Boyle will remain certain of are matters of fact: “I dare speak confidently and positively of very few things, except Matters of Fact” (BW, 2:19).