The expression, “truth of God,” is ambiguous, and must be considered under the specific terms which set forth its various meanings.
I. His Verity. He is True God. By this is meant, the exact correspondence of the nature of God with the ideal of absolute perfection. The foundation of that ideal may be indeterminable. But, whether it is in the nature of God himself, or in his will proceeding from his nature, or in eternal principles of the fit and the necessary and the right, which exactly coincide with that nature, God and that ideal must be perfect counterparts. That ideal can only be partially comprehended by any of his creatures, because of their imperfections; but it is known by God in all its supreme excellence, and his nature must fully correspond to it as thus known. Otherwise he would not be God.
It is in this aspect of God’s truth, that the Scriptures call him the true God. See 2 Chron 15:3; Jer 10:10; John 17:3; 1 Thess 1:9; 1 John 5:20; Rev 3:7.
II. His Veracity. By this is meant, God’s truthfulness or incapacity to deceive. It is an attribute of his nature, which, like his power, exists, and makes him what he is, even though there be no outward relation to it. By virtue of it, he is the source of all truth, not moral only, but even mathematical.
In its relation to God’s creatures, it is the foundation of their confidence in the knowledge obtained through the use of their own faculties, whether by intuition, observation or reason. Whatever imperfection there is in such knowledge, is perceived to be due to the creature, and not to God the creator. Upon it is also based belief in the revelations God makes to man of facts beyond the attainment of merely human power.
The Scriptures affirm the veracity of God in the strongest terms. In addition to its assertion in numerous passages, we are told, Ps 108:4, that his “truth reacheth unto the skies.” In Titus 1:2, he is called “God, who cannot lie.”
III. His Faithfulness. This consists in the truth of God viewed in its relation to his purposes whether secret, or revealed. When revealed, these become either promises, or threats. But as promises, the ground upon which these purposes must be fulfilled is, not any obligation to the creature, for God can come under none, but simply because of his own faithfulness to his purposes. Hence his faithfulness demands equally the performance of his threatenings, as of his promises.
This faithfulness is based upon the veracity of his nature considered above. It is by virtue of that veracity, that God must be faithful; yet the faithfulness is a new aspect, in which God’s truthfulness appears.
This faithfulness is the ground both of hope and of fear. In the Scriptures it is more frequently presented as a reason for hope and trust. But it is also the foundation of belief in future judgment and punishment. The faithful God has been true to his threatenings, as well as his promises. His faithfulness assures us that he will so continue.
Boyce, James (1887-06-01). Abstract of Systematic Theology (p. 79). Kindle Edition.