are so, and no ground for doubting remains, I
scarcely believe, nevertheless, that, without a proof derived from
experience, men will be induced calmly to weigh what has been said, so
firmly are they persuaded that, solely at the bidding of the mind, the
body moves or rests, and does a number of things which depend upon the
will of the mind alone, and upon the power of thought. For what the body
can do no one has hitherto determined, that is to say, experience has
taught no one hitherto what the body, without being determined by the
mind, can do and what it cannot do from the laws of Nature alone, in so
far as Nature is considered merely as corporeal. For no one as yet has
understood the structure of the body so accurately as to be able to
explain all its functions, not to mention the fact that many things are
observed in brutes which far surpass human sagacity, and that
sleep-walkers in their sleep do very many things which they dare not do
when awake; all this showing that the body itself can do many things
from the laws of its own nature alone at which the mind belonging to
that body is amazed.

Again, nobody knows by what means or by what method the mind moves the
body, nor how many degrees of motion it can communicate to the body, nor
with what speed it can move the body. So that it follows that when men
say that this or that action of the body springs from the mind which has
commanded over the body, they do not know what they say, and they do
nothing but confess with pretentious words that they know nothing about
the cause of the action, and see nothing in it to wonder at.

But they will say, that whether they know or do not know by what means
the mind moves the body, it is nevertheless in their experience that if
the mind were not fit for thinking the body would be inert. They say,
again, it is in their experience that the mind alone has power both to
speak and be silent, and to do many other things which they therefore
think to be dependent on a decree of the mind.

But with regard to the first assertion, I ask them if experience does
not also teach that if the body be sluggish the mind at the same time is
not fit for thinking? When the body is asleep, the mind slumbers with
it, and has not the power to think, as it has when the body is awake.
Again, I believe that all have discovered that the mind is not always
equally fitted for thinking about the same subject, but in proportion to
the fitness of the body fo