is caused in the brain, which affects the mind with
the sensation of animal joy (LAETITIA ANIMALIS).
On the same principle, when the blood is so thick
that it flows but sparingly into the ventricles of
the heart, and is not there sufficiently dilated,
it excites in the same nerves a motion quite different
from the preceding, which, communicated to the brain,
gives to the mind the sensation of sadness, although
the mind itself is perhaps ignorant of the cause of
its sadness. And all the other causes which move
these nerves in the same way may also give to the
mind the same sensation. But the other movements
of the same nerves produce other effects, as the feelings
of love, hate, fear, anger,
etc., as far as they
are merely affections or passions of the mind; in
other words, as far as they are confused thoughts which
the mind has not from itself alone, but from its being
closely joined to the body, from which it receives
impressions; for there is the widest difference between
these passions and the distinct thoughts which we
have of what ought to be loved, or chosen, or shunned,
etc., [although these are often enough found
together]. The natural appetites, as hunger,
thirst, and the others, are likewise sensations excited
in the mind by means of the nerves of the stomach,
fauces, and other parts, and are entirely different
from the will which we have to eat, drink, [and to
do all that which we think proper for the conservation
of our body]; but, because this will or appetition
almost always accompanies them, they are therefore
named appetites.
CXCI. Of the external senses; and first
of touch.
We commonly reckon the external senses five in number,
because there are as many different kinds of objects
which move the nerves and their organs, and an equal
number of kinds of confused thoughts excited in the
soul by these emotions. In the first place, the
nerves terminating in the skin of the whole body can
be touched through this medium by any terrene objects
whatever, and moved by these wholes, in one way by
their hardness, in another by their gravity, in a
third by their heat, in a fourth by their humidity,
etc.—and in as many diverse modes as
they are either moved or hindered from their ordinary
motion, to that extent are diverse sensations excited
in the mind, from which a corresponding number of
tactile qualities derive their appellations. Besides
this, when these nerves are moved a little more powerfully
than usual, but not nevertheless to the degree by
which our body is in any way hurt, there thus arises
a sensation of titillation, which is naturally agreeable
to the mind, because it testifies to it of the powers
of the body with which it is joined, [in that the
latter can suffer the action causing this titillation,
without being hurt]. But if this action be strong
enough to hurt our body in any way, this gives to
our mind the sensation of pain. And we thus see
why corporeal pleasure and pain, although sensations
of quite an opposite character, arise nevertheless
from causes nearly alike.