Summing up the lessons of the final book of his Essay Concerning Human Understanding, Locke describes two ‘ways to enlarge our Knowledge, as far as we are capable.’ One involves the cultivation of our capacity for demonstrative reasoning, the other the proper framing of the ideas from which any such reasoning must issue and on which mere ‘experimental Knowledge’ (IV .iii.29: 560) is likewise founded. Under the latter heading, we are urged to aim not only for ‘clear’ and ‘distinct’ ideas, but also for ‘perfect’ ones. Finally, a laconic insertion in the fourth edition specifies how the perfection of one class of ideas is to be pursued:
And if they be specific Ideas of Substances, we should endeavor also to make them as complete as we can, whereby I mean, that we should put together as many simple Ideas, as being constantly observed to co-exist, may perfectly determine the Species…. (IV.xii.14: 648)