Summa contra Gentiles1.62 Chapter LXII. That the divine truth is the first and supreme truth

From what has been proved it clearly follows that the divine truth is the first and supreme truth.

For the disposition of things in truth is as their disposition in being, according to the Philosopher (2 Metaph.), and this because truth and being are mutually consequent upon one another; since the true is when that is said to be which is, and that not to be, whicK is not. Now God's being is first and most perfect. Therefore His truth is also first and supreme.

Again. That which belongs to a thing essentially belongs thereto most perfectly. Now truth is ascribed to God essentially, as we have proved. Therefore His truth is the supreme and first truth.

Further. Truth is in our intellect through the latter being equated to the thing understood. Now the cause of equality is unity, as stated in 5 Metaph. Since then in the divine intellect, intellect and thing understood are absolutely the same, His truth must be the first and supreme truth.

Moreover. That which is the measure in any genus must be the most perfect in that genus, wherefore all colours are measured by white. Now the divine truth is the measure of all truth. For the truth of our intellect is measured by the thing that is outside the mind, since our intellect is said to be true from the very fact that it accords with the thing. And the truth of a thing is measured according to the divine intellect which is the cause of things, as we shall prove further on: even as the truth of art-products is measured by the art of the craftsman: for then is a casket true when it accords with art. Also, since God is the first intellect and the first intelligible, it follows that the truth of every intellect must be measured by His truth: if each thing is measured by the first in its genus, as the Philosopher teaches in 10 Metaph. Hence the divine truth is the first, supreme and most perfect truth.