— 558 —
Secondly, want of a discoverable connexion between Ideas we have.
      §28. Secondly, What a small part of the substantial Beings, that are
in the Universe, the want of Ideas leave open to our Knowledge, we
have seen. In the next place, another cause of Ignorance, of no less
moment, is a want of a discoverable Connection between those Ideas
which we have. For wherever we want that, we are utterly un-
capable of universal and certain Knowledge; and are, as in the
former case, left only to Observation and Experiment: which how
narrow and confined it is, how far from general Knowledge, we
need not be told. I shall give some few instances of this cause of our
Ignorance and so leave it. ’Tis evident that the bulk, figure, and
motion of several Bodies about us, produce in us several Sensations,
as of Colours, Sounds, Tastes, Smells, Pleasure and Pain, etc. These
mechanical Affections of Bodies, having no affinity at all with those
— 559 —
Ideas, they produce in us, (there being no conceivable connexion
between any impulse of any sort of Body, and any perception of a
Colour, or Smell, which we find in our Minds) we can have no
distinct knowledge of such Operations beyond our Experience;
and can reason no otherwise about them, than as effects produced
by the appointment of an infinitely Wise Agent, which perfectly
surpass our Comprehensions. As the Ideas of sensible secondary
Qualities, which we have in our Minds, can, by us, be no way de-
duced from bodily Causes, nor any correspondence or connexion be
found between them and those primary Qualities which (Experience
shews us) produce them in us; so on the other side, the Operation
of our Minds upon our Bodies is as unconceivable. How any thought
should produce a motion in Body is as remote from the nature of our
Ideas, as how any Body should produce any Thought in the Mind.
That it is so, if Experience did not convince us, the Consideration
of the Things themselves would never be able, in the least, to dis-
cover to us. These, and the like, though they have a constant and
regular connexion, in the ordinary course of Things: yet that
connexion being not discoverable in the Ideas themselves, which
appearing to have no necessary dependance one on another, we can
attribute their connexion to nothing else, but the arbitrary Deter-
mination of that All-wise Agent, who has made them to be, and to
operate as they do, in a way wholly above our weak Understandings
to conceive.
Locke Hum IV, 3, §28, pp. 558-559