— 133 —
      §4. If it were the design of my present Undertaking, to enquire
into the natural Causes and manner of Perception, I should offer this
as a reason why a privative cause might, in some cases at least, produce
a positive Idea, viz. That all Sensation being produced in us, only
by different degrees and modes of Motion in our animal Spirits,
variously agitated by external Objects, the abatement of any
former motion, must as necessarily produce a new sensation, as
the variation or increase of it; and so introduce a new Idea, which
depends only on a different motion of the animal Spirits in that
Organ.
Locke Hum II, 8, §4, p. 133