5. Secondly, Because we find that an idea from actual sensation, and another from memory, are very distinct
perceptions.
II. Because sometimes I find that I cannot avoid the having those ideas produced in my mind. For
though, when my eyes are shut, or windows fast, I can at pleasure recall to my mind the ideas of light, or the sun,
which former sensations had lodged in my memory; so I can at pleasure lay by that idea, and take into my view
that of the smell of a rose, or taste of sugar. But, if I turn my eyes at noon towards the sun, I cannot avoid the
ideas which the light or sun then produces in me. So that there is a manifest difference between the ideas laid up
in my memory, (over which, if they were there only, I should have constantly the same power to dispose of them,
and lay them by at pleasure,) and those which force themselves upon me, and I cannot avoid having. And
therefore it must needs be some exterior cause, and the brisk acting of some objects without me, whose efficacy I
cannot resist, that produces those ideas in my mind, whether I will or no. Besides, there is nobody who doth not
perceive the difference in himself between contemplating the sun, as he hath the idea of it in his memory, and
actually looking upon it: of which two, his perception is so distinct, that few of his ideas are more distinguishable
one from another. And therefore he hath certain knowledge that they are not both memory, or the actions of his
mind, and fancies only within him; but that actual seeing hath a cause without.
