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Principles of Human Knowledge

101. OF NATURAL PHILOSOPHY AND MATHEMATICS.--The two great provinces of
speculative science conversant about ideas received from sense, are Natural Philosophy and
Mathematics; with regard to each of these I shall make some observations. And first I shall say
somewhat of Natural Philosophy. On this subject it is that the sceptics triumph. All that stock of
arguments they produce to depreciate our faculties and make mankind appear ignorant and low,
are drawn principally from this head, namely, that we are under an invincible blindness as to the
true and real nature of things. This they exaggerate, and love to enlarge on. We are miserably
bantered, say they, by our senses, and amused only with the outside and show of things. The
real essence, the internal qualities and constitution of every the meanest object, is hid from our
view; something there is in every drop of water, every grain of sand, which it is beyond the
power of human understanding to fathom or comprehend. But, it is evident from what has been
shown that all this complaint is groundless, and that we are influenced by false principles to that
degree as to mistrust our senses, and think we know nothing of those things which we perfectly
102. One great inducement to our pronouncing ourselves ignorant of the nature of things is the
current opinion that everything includes within itself the cause of its properties; or that there is in
each object an inward essence which is the source whence its discernible qualities flow, and
whereon they depend. Some have pretended to account for appearances by occult qualities, but
of late they are mostly resolved into mechanical causes, to wit. the figure, motion, weight, and
suchlike qualities, of insensible particles; whereas, in truth, there is no other agent or efficient
cause than spirit, it being evident that motion, as well as all other ideas, is perfectly inert. See
sect. 25. Hence, to endeavour to explain the production of colours or sounds, by figure, motion,
magnitude, and the like, must needs be labour in vain. And accordingly we see the attempts of
that kind are not at all satisfactory. Which may be said in general of those instances wherein
one idea or quality is assigned for the cause of another. I need not say how many hypotheses
and speculations are left out, and how much the study of nature is abridged by this doctrine.
mechanical principle now in vogue is attraction. That a stone falls to the earth, or the sea swells
towards the moon, may to some appear sufficiently explained thereby. But how are we
enlightened by being told this is done by attraction? Is it that that word signifies the manner of
the tendency, and that it is by the mutual drawing of bodies instead of their being impelled or
protruded towards each other? But, nothing is determined of the manner or action, and it may
as truly (for aught we know) be termed "impulse," or "protrusion," as "attraction." Again, the
parts of steel we see cohere firmly together, and this also is accounted for by attraction; but, in
this as in the other instances, I do not perceive that anything is signified besides the effect itself;
for as to the manner of the action whereby it is produced, or the cause which produces it, these
are not so much as aimed at.
104. Indeed, if we take a view of the several phenomena, and compare them together, we may
observe some likeness and conformity between them. For example, in the falling of a stone to
the ground, in the rising of the sea towards the moon, in cohesion, crystallization, etc, there is