Summa contra Gentiles1.41 Chapter XLI. That God is the sovereign good

From this it is proved that God is the sovereign good. For the universal good stands far above any particular good, even as the good of the nation is greater than the good of an individual: since the goodness and perfection of the whole stand above the goodness and perfection of the part. Now the divine goodness of God is compared to all other things as the universal good to the particular, for He is the good of every good, as we have proved. Therefore He is the sovereign good.

Moreover. That which is predicated essentially is said more truly than that which is predicated by participation. Now God is good by His essence; and other things, by participation, as shown above. Therefore He is the sovereign good.

Again. The greatest in any genus is the cause of others in that genus: since the cause is greater than its effect. Now all things derive their ratio of goodness from God, as we have shown. Therefore He is the sovereign good.

Moreover. Just as that is more white which has less admixture of black, so that is better which has less admixture of evil. Now God is most of all unmixed with evil, since in Him there can be no evil, neither in act nor in potentiality, and this becomes Him by His very nature, as we have proved. Therefore He is the sovereign good.

Hence it is said (1 Kings ii. 2): There is none holy as the Lord is.