Though the examining and judging of Ideas by themselves, their Names being quite laid aside, be the best and surest way to clear and distinct Knowledge : yet through the prevailing custom of using Sounds of ideas, I think it is very seldom practised. Every one may observe how common it is for Names to be made use of, instead of the Ideas themselves, even when Men think and reason within their Breasts; especially if the Ideas be very complex, and made up of a great collection of simple ones. This makes the consideration of Words and Propositions, so necessary a part of the Treatise of Knowledge, that 'tis very hard to speak intelligibly of the one, without explaining the other.