If men can be ignorant of what is innate, certainty is not described by innate principles.
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“are so far from being innate, that it is not every studious or thinking man, much less every one that is born, in whom they are to be found clear and distinct; and that one of them, which of all others seems most likely to be innate, is not so, (I mean the idea of God,) I think, in the next chapter, will appear very evident to any considering man. 13. If men can be ignorant of what is innate, certainty is not described by innate principles. From what has been said, I think we may safely conclude that whatever practical rule is in any place generally and with allowance broken, cannot be supposed innate; it being impossible that men should, without shame or fear, confidently and serenely, break a rule which they could not but evidently know that God had set up, and would certainly punish the breach of,” source