An Essay Concerning Humane Understanding, Volume 2: MDCXC, Based on the 2nd Edition, Books 3 and 4
John Locke · en
Thirdly, That we cannot have an INTUITIVE KNOWLEDGE that shall extend
itself to all our ideas, and all that we would know about them; because
we cannot examine and perceive all the relations they have one to
another, by juxta-position, or an immediate comparison one with another.
Thus, having the ideas of an obtuse and an acute angled triangle, both
drawn from equal bases, and between parallels, I can, by intuitive
knowledge, perceive the one not to be the other, but cannot that
way know whether they be equal or no; because their agreement or
disagreement in equality can never be perceived by an immediate
comparing them: the difference of figure makes their parts incapable
of an exact immediate application; and therefore there is need of some
intervening qualities to measure them by, which is demonstration, or
rational knowledge.
4. Fourthly, Nor does Demonstrative Knowledge.
Fourthly, It follows, also, from what is above observed, that our
RATIONAL KNOWLEDGE cannot reach to the whole extent of our ideas:
because between two different ideas we would examine, we cannot always
find such mediums as we can connect one to another with an intuitive
knowledge in all the parts of the deduction; and wherever that fails, we
come short of knowledge and demonstration.
5. Fifthly, Sensitive Knowledge narrower than either.
Fifthly, SENSITIVE KNOWLEDGE reaching no further than the existence of
things actually present to our senses, is yet much narrower than either
of the former.
6. Sixthly, Our Knowledge, therefore narrower than our Ideas.