In God there is Love; for the motion of will tends of itself to good, and only accidentally to evil. Moreover, that which is of itself is prior to that which is by something else, and the general is prior to the particular; hence love, which regards good in general, whether possessed or not possessed, is the first act of the will - presupposed as the root of all other movements of desire; and since Will exists in God, there must be Love also.
God, therefore, loves all things inasmuch as they exist, for existence is good, and since His Will is the Cause of all things He wills them to be good. But love is not the same in God as it is in us; for when God loves He infuses and creates goodness in things; whereas we are moved to love by the good which we find in them.
God loves irrational creatures with a Love of Pleasure, inasmuch as He has subordinated them to the use of rational creatures; for Himself He has no need of them and nothing accrues to Him from them.
Inasmuch as God loves all things by one single and simple act, that act is not said to be more or less intense on the part of Him Who loves; but as regards the good which He wills to the loved, He loves some more than others. And because His Will is the Cause of good in creatures, one is not better than another except as being more loved by God; while God always loves the best, inasmuch as His Will is the Cause of their goodness.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni