evidence of experiments for the sake of dreams and vain fictions of
our own devising; nor are we to recede from the analogy of Nature,
which is wont to be simple and always consonant to itself. We in
no other way know the extension of bodies than by our senses, nor
do these reach it in all bodies; but because we perceive extension
in all that are sensible, therefore we ascribe it universally to all
others also. That abundance of bodies are hard we learn by
experience; and because the hardness of the whole arises from the
hardness of the parts, we therefore justly infer the hardness of the
undivided particles, not only of the bodies we feel, but of all others.
That all bodies are impenetrable, we gather not from reason, but
from sensation. The bodies which we handle we find impenetrable,
and thence conclude impenetrability to be a universal property of
all bodies whatsoever. That all bodies are movable and endowed
with certain powers (which we call the inertia) of persevering in
their motion, or in their rest, we only infer from the like properties
observed in the bodies which we have seen. The extension, hard-
ness, impenetrability, mobility, and inertia of the whole result
from the extension, hardness, impenetrability, mobility, and inertia
of the parts; and hence we conclude the least particles of all bodies
to be also all extended, and hard and impenetrable, and movable,
and endowed with their proper inertia. And this is the foundation
of all philosophy. Moreover, that the divided but contiguous par-
ticles of bodies may be separated from one another is a matter of
observation; and, in the particles that remain undivided, our minds
are able to distinguish yet lesser parts, as is mathematically
demonstrated. But whether the parts so distinguished and not yet
divided may, by the powers of Nature, be actually divided and
separated from one another we cannot certainly determine. Yet
had we the proof of but one experiment that any undivided par-
ticle, in breaking a hard and solid body, suffered a division, we
might by virtue of this rule conclude that the undivided as well
as the divided particles may be divided and actually separated to
infinity.

Lastly, if it universally appears, by experiments and astronom-
ical observations, that all bodies about the earth gravitate toward
the earth, and that in proportion to the quantity of matter which

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