val in several places. Neither does he think it necessary, that
those intervals should be fill'd up; nor unconceivable, that there should
be no Body between two Bodies; which touch not one another. And when 'tis
said, that those intervals cannot be conceived without Extension, and that
consequently there are Bodies that replenish them, he frankly pronounces
that not to be true; and affirms, that though it may be said, that between
two Bodies, which touch not one another, other Bodies may be placed of so
or so many feet, &c: yet ought it not to be inferred, that therefore they
_are_ there, but onely, that they are thus placed, that there _may_ be put
between them so many Bodies, as joyned together would compose an Extension
of so many feet. So that one conceives onely, that Bodies _may_ be placed
there, but not that they _are_ there: and as we can have an _Idea_ of many
Bodies, though none of them be in being; so we can conceive, that some
Bodies _may_ be put between others, where really there are none. And when
'tis alledged, that if all the Bodies, that fill a vessel full, were
destroyed, the sides of the vessel would be closed together; He professes,
he understands not that ratiocination, nor can conceive, what one Body does
to the subsistence of another, more than to sustain themselves mutually,
when they are thrust by the neighbouring ones: and therefore sees not, why
the sides of the vessel should close, if nothing did thrust them together;
but understands clearly, that two Bodies may well subsist so far from one
another, that one might place a great many Bodies between them, or none at
all, and yet they neither approach to, not recoil from one another. {308}

2. In the _Second_, he examines the _Changes_, which he knows in Matter,
and makes it his business to explicate all those that respect _Quantity_,
_Qualities_ and _Forms_, by _Local Motion_, esteeming that needs no other.

3. In the _third_, he explains the Motion of _Artificial_ Engins, and that
of _Natural_ ones, by one and the same Cause; endeavouring among other
things to shew, that the Body of an Animal is moved after the same manner
with a Watch. That cause of motion he makes the _Materia Subtilis_; and the
finer or subtiler that is, the better and fitter he conceives it to be to
preserve Motion.

4. In the _Fourth_, he teaches, that though Experience seems to evince,
that the Soul moves the Body, and that one Body moves an other; yet there
is nothing b