duce its necessary effects,
either as regards order or quantity. Seeing that a force impels an
object which it overcomes a distance of one hundred arms' length, and
if in obeying this law it meets with resistance, thou hast ordained
that the force of the shock will cause afresh a further movement, which
in its various bounds recuperates the whole sum of the distance it
should have travelled. And if you measure the distance {148}
accomplished by the aforesaid bounds you will find that they equal the
length of distance through which a similar object set in motion by an
equal force would travel freely through the air.

15.

Every action must be caused by motion.

16.

Motion is the cause of all life.

[Sidenote: Of Force]

17.

What is force? Force, I say, is a spiritual virtue, an invisible
power, which by accidental external violence is caused by motion, and
communicated and infused into bodies which are inert by nature, giving
them an active life of marvellous power.

18.

What is force? I say that force is a spiritual, incorporate and
invisible power, which for a brief duration is produced in bodies that
by accidental violence are displaced from their natural state of
inertia.

[Sidenote: Origin of Force]

19.

Force arises from dearth or abundance; it is the child of physical
motion and the grandchild of spiritual motion, and the mother and
origin of gravity. Gravity is confined to the elements of {149} water
and earth, and this force is infinite, because infinite worlds could be
moved by it if instruments could be made by which the force could be
generated. Force, with physical motion, and gravity, with resistance,
are the four accidental powers by which all mortal things live and die.
Force has its origin in spiritual motion, and this motion, flowing
through the limbs of sentient animals, enlarges their muscles, and thus
enlarged the muscles are shrunk in length and contract the tendons with
which they are connected, and this is the cause of the strength in
human limbs. The quality and quantity of the strength of a man can
generate a further force, which will increase in proportion to the
duration of the motions produced by them.

[Sidenote: Aspects of Force]

20.

Gravity, force and casual motion together with resistance are the four
external powers by which all the visible actions of man live and die.

[Sidenote: Of Inertia]

21.

A motion tends to be continuous; a