No More Learning

So, for example, when I           the
Nature of a Triangle, it plainly appears to me (as understanding the
Principles of Geometry) that its three Angles are equal to two right
ones; And this I must of necessity think _True_ as long as I attend to
the _Demonstration_ thereof; but as soon as ever I withdraw my Mind from
the _Consideration_ of its _Proof_ (altho I remember that I have once
_Clearly_ perceived it) yet perhaps I may _doubt_ of Its _Truth_, being
as yet _Ignorant_ of a _God_; For I may perswade my self, that I am so
framed by _Nature_, as to be _deceived_ in those things which I imagine
my self to perceive most _evidently_, Especially when I recollect, that
heretofore I have often accounted many things _True_ and _Certain_, which
afterward upon other Reasons I have Judged as False.