, The probabilities we have hitherto mentioned are only such
as concern matter of fact, and such things as are capable of observation
and testimony. There remains that other sort, concerning which men
entertain opinions with variety of assent, though THE THINGS BE SUCH,
THAT FALLING NOT UNDER THE REACH OF OUR SENSES, THEY ARE NOT CAPABLE OF
TESTIMONY. Such are, 1. The existence, nature and operations of finite
immaterial beings without us; as spirits, angels, devils, &c. Or the
existence of material beings which, either for their smallness in
themselves or remoteness from us, our senses cannot take notice of--as,
whether there be any plants, animals, and intelligent inhabitants in
the planets, and other mansions of the vast universe. 2. Concerning
the manner of operation in most parts of the works of nature: wherein,
though we see the sensible effects, yet their causes are unknown, and we
perceive not the ways and manner how they are produced. We see animals
are generated, nourished, and move; the loadstone draws iron; and the
parts of a candle, successively melting, turn into flame, and give us
both light and heat. These and the like effects we see and know: but the
causes that operate, and the manner they are produced in, we can only
guess and probably conjecture. For these and the like, coming not within
the scrutiny of human senses, cannot be examined by them, or be attested
by anybody; and therefore can appear more or less probable, only as they
more or less agree to truths that are established in our minds, and as
they hold proportion to other parts of our knowledge and observation.
ANALOGY in these matters is the only help we have, and it is from that
alone we draw all our grounds of probability. Thus, observing that the
bare rubbing of two bodies violently one upon another, produces heat,
and very often fire itself, we have reason to think, that what we call
HEAT and FIRE consists in a violent agitation of the imperceptible
minute parts of the burning matter. Observing likewise that the
different refractions of pellucid bodies produce in our eyes the
different appearances of several colours; and also, that the different
ranging and laying the superficial parts of several bodies, as of
velvet, watered silk, &c., does the like, we think it probable that
the COLOUR and shining of bodies is in them nothing but the different
arrangement and refraction of their minute and insensible parts. Thus,
finding in all parts of