Boyle improved the pneumatic engine invented by Otto Guericke, and was thereby enabled to make several new and curious experiments on the air, as well as on other bodies: His chemistry is much admired by those who are acquainted with that art: His hydrostatics contain a greater mixture of reasoning and invention with experiment than any other of his works; but his reasoning is still remote from that boldness and temerity which had led astray so many philosophers. Boyle was a great partisan of the mechanical philosophy; a theory which, by discovering some of the secrets of nature, and allowing us to imagine the rest, is so agreeable to the natural vanity and curiosity of man.
(This is in the context of discussing the 'Manners and sciences' of the reign of James II.) This should be compared to Hume's justification of philosophical inquiry in Treatise 1.4.7 (scroll down) and the last section of Book II, on curiosity, which describes curiosity or the love of truth as the itch (to put it in a rough and simplistic form) to find useful solutions to interesting problems. The idea, I take it, is that some theories satisfy because (1) they provide useful or interesting solutions to problems that are considered important; and (2) they allow scientists to make a name for themselves as discoverers (vanity or ambition). Immediately after this, Hume goes on to claim Newton as a skeptic: his work is superior to that of the mechanical philosophers in that we can't, as in the case of the mechanical philosophy, pretend or fool ourselves into thinking that we know the ultimate causes.
