will always keep that motion or
change, that is, the same swiftness and the same direction, unless
something happens to hinder it_. (M. Leibniz, ibid.)

'Everyone clearly sees that this atom, whether it moves by an innate power,
as Democritus and Epicurus would have it, or by a power received from the
Creator, will always move in the same line equally and after a uniform
manner, without ever turning or going back. Epicurus was laughed at, when
he invented the motion of declination; it was a needless supposition, which
he wanted in order to get out of the labyrinth of a fatal necessity; and he
could give no reason for this new part of his system. It was inconsistent
with the clearest notions of our minds: for it is evident that an atom
which describes a straight line for the space of two days cannot turn away
at the beginning of a third, unless it meets with some obstacle, or has a
mind all of a sudden to go out of its road, or contains some spring which
begins to play at that very moment. The first of these reasons cannot be
admitted in a vacuum. The second is impossible, since an atom has not the
faculty of thinking. And the third is likewise impossible in a corpuscle
that is a perfect unity. I must make some use of all this.

'VI. Caesar's soul is a being to which unity belongs in a strict sense. The
faculty of producing thoughts is a property of its nature (so M. Leibniz),
which it has received from God, both as to possession and exercise. If the
first thought it produces is a sense of pleasure, there is no reason why
the second should not likewise be a sense of pleasure; for when the total
cause of an effect remains the same, the effect cannot be altered. Now this
soul, at the second moment of its existence, does not receive a new faculty
of thinking; it only preserves the faculty it had at the first moment, and
it is as independent of the concourse of any other cause at the second [43]
moment as it was at the first. It must therefore produce again at the
second moment the same thought it had produced just before. If it be
objected that it ought to be in a state of change, and that it would not be
in such a state, in the case that I have supposed; I answer that its change
will be like the change of the atom; for an atom which continually moves in
the same line acquires a new situation at every moment, but it is like the
preceding situation. A soul may therefore continue in its state of change,
if it does but produce