"God is love" (John 4:16).

_I answer that,_ We must needs assert that in God there is love:
because love is the first movement of the will and of every
appetitive faculty. For since the acts of the will and of every
appetitive faculty tend towards good and evil, as to their proper
objects: and since good is essentially and especially the object of
the will and the appetite, whereas evil is only the object
secondarily and indirectly, as opposed to good; it follows that the
acts of the will and appetite that regard good must naturally be
prior to those that regard evil; thus, for instance, joy is prior to
sorrow, love to hate: because what exists of itself is always prior
to that which exists through another. Again, the more universal is
naturally prior to what is less so. Hence the intellect is first
directed to universal truth; and in the second place to particular
and special truths. Now there are certain acts of the will and
appetite that regard good under some special condition, as joy and
delight regard good present and possessed; whereas desire and hope
regard good not as yet possessed. Love, however, regards good
universally, whether possessed or not. Hence love is naturally the
first act of the will and appetite; for which reason all the other
appetite movements presuppose love, as their root and origin. For
nobody desires anything nor rejoices in anything, except as a good
that is loved: nor is anything an object of hate except as opposed to
the object of love. Similarly, it is clear that sorrow, and other
things like to it, must be referred to love as to their first
principle. Hence, in whomsoever there is will and appetite, there
must also be love: since if the first is wanting, all that follows is
also wanting. Now it has been shown that will is in God (Q. 19, A.
1), and hence we must attribute love to Him.

Reply Obj. 1: The cognitive faculty does not move except through the
medium of the appetitive: and just as in ourselves the universal
reason moves through the medium of the particular reason, as stated
in _De Anima_ iii, 58, 75, so in ourselves the intellectual appetite,
or the will as it is called, moves through the medium of the
sensitive appetite. Hence, in us the sensitive appetite is the
proximate motive-force of our bodies. Some bodily change therefore
always accompanies an act of the sensitive appetite, and this change
affects especially the heart, which, as the Philosopher says (De
part. anima