gent," and

"can be the effect of nothing else than the wisdom and skill
of a powerful ever-living Agent who, being in all places, is
more able by his will to move the bodies within his boundless
uniform _sensorium_, and thereby to form and reform the parts
of the universe, than we are by our will to move the parts of
our own bodies."[233:7]

But by the side of these statements must be set his famous disclaimer,
"_hypotheses non fingo_." In his capacity of natural philosopher he did
not seek to explain motions, but only to describe them. Disbelieving as
he did in action at a distance, he saw no possibility of explanation
short of a reference of them to God; but such "hypotheses" he thought to
be no proper concern of science. As a consequence, the mathematical
formulation of motions came, through him, to be regarded as the entire
content of mechanics. The notion of an efficient cause of motion is
still suggested by the term _force_, but even this term within the
system of mechanics refers always to a definite amount of motion, or
measurement of relative motion. And the same is true of _attraction_,
_action_, _reaction_, and the like. The further explanation of motion,
the definition of a virtue or potency that produces it, first a
neglected problem, then an irrelevant problem, is finally, for a
naturalistic philosophy in which this progression is completed, an
insoluble problem. For the sequel to this purely descriptive procedure
on the part of science is the disavowal of "metaphysics" by those who
will have no philosophy but science. Thus the scientific conservatism of
Newton has led to the positivistic and agnostic phase of naturalism. But
a further treatment of this development must be reserved until the issue
of epistemology shall have been definitely raised.

A different emphasis within the general mechanical scheme, attaching
especial importance to the conceptions of force and energy, has led to a
rival tendency in science and a contrasting type of naturalism. The
mechanical hypotheses hitherto described are all of a simple and readily
depicted type. They suggest an imagery quite in accord with common-sense
and with observation of the motions of great masses like the planets.
Material particles are conceived to move within a containing space; the
motions of corpuscles, atoms, or the minute parts of ether, differing
only in degree from those of visible bodies. The whole physical
univ