there is no centrifugal force, which, nevertheless, in
that which is true or absolute, is proportional to the quantity of
motion.

112. MOTION, WHETHER REAL OR APPARENT, RELATIVE.--But, notwithstanding
what has been said, I must confess it does not appear to me that
there can be any motion other than relative; so that to conceive
motion there must be at least conceived two bodies, whereof the
distance or position in regard to each other is varied. Hence, if there
was one only body in being it could not possibly be moved. This seems
evident, in that the idea I have of motion doth necessarily include
relation.

113. APPARENT MOTION DENIED.--But, though in every motion it be
necessary to conceive more bodies than one, yet it may be that one
only is moved, namely, that on which the force causing the change
in the distance or situation of the bodies, is impressed. For, however
some may define relative motion, so as to term that body moved
which changes its distance from some other body, whether the force
or action causing that change were impressed on it or no, yet as
relative motion is that which is perceived by sense, and regarded in
the ordinary affairs of life, it should seem that every man of common
sense knows what it is as well as the best philosopher. Now, I ask any
one whether, in his sense of motion as he walks along the streets, the
stones he passes over may be said to move, because they change distance
with his feet? To me it appears that though motion includes a relation of
one thing to another, yet it is not necessary that each term of the
relation be denominated from it. As a man may think of somewhat which
does not think, so a body may be moved to or from another body which is
not therefore itself in motion.

114. As the place happens to be variously defined, the motion which is
related to it varies. A man in a ship may be said to be quiescent with
relation to the sides of the vessel, and yet move with relation to the
land. Or he may move eastward in respect of the one, and westward in
respect of the other. In the common affairs of life men never go beyond
the earth to define the place of any body; and what is quiescent in
respect of that is accounted absolutely to be so. But philosophers, who
have a greater extent of thought, and juster notions of the system of
things, discover even the earth itself to be moved. In order therefore to
fix their notions they seem to conceive the corporeal world as finite,