From the SUMMA THEOLOGICA:
Question 16. Truth
- Does truth reside in the thing, or only in the intellect?
- Does it reside only in the intellect composing and dividing?
- The comparison of the true to being
- The comparison of the true to the good
- Is God truth?
- Are all things true by one truth, or by many?
- The eternity of truth
- The unchangeableness of truth
Article 1. Whether truth resides only in the intellect?
Objection 1. It seems that truth does not reside only in the intellect, but rather in things. For Augustine (Soliloq. ii, 5) condemns this definition of truth, “That is true which is seen”; since it would follow that stones hidden in the bosom of the earth would not be true stones, as they are not seen. He also condemns the following, “That is true which is as it appears to the knower, who is willing and able to know,” for hence it would follow that nothing would be true, unless someone could know it. Therefore he defines truth thus: “That is true which is.” It seems, then, that truth resides in things, and not in the intellect.
Objection 2. Further, whatever is true, is true by reason of truth. If, then, truth is only in the intellect, nothing will be true except in so far as it is understood. But this is the error of the ancient philosophers, who said that whatever seems to be true is so. Consequently mutual contradictories seem to be true as seen by different persons at the same time.
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