Truth, goodness and beauty are not three tastes nor three departments. The classical tradition called them transcendentals: three names for one reality.
What the transcendentals are
Transcendentals are properties that accompany every being, cutting across (transcending) all categories. Everything that exists is, insofar as it exists, one, true, good and beautiful. They are not additions to being; they are being itself considered from different angles.
When I say something is true, I say that it is intelligible, that it corresponds to a mind. When I say it is good, I say that it is desirable, worthy of being wanted. And the union of the true and the good, shining forth, is the beautiful: that is why what is true and good tends also to be beautiful.
Why this topples the relativism of the good
If the good is a transcendental, then it is not personal taste: good is what corresponds to a truth about what the human being is and what it needs to flourish, exactly as a statement is true when it corresponds to the real. To deny the truth of the good is not to be tolerant, it is to lose the criterion for saying that something is unjust. At the height of this tradition, the three transcendentals meet again in their common origin: a Reason that thought the world.
In-depth study
Church History Course, with Prof. Dr. Rodrigo Bitencourt
In-depth reading of the work of Daniel Rops, where Thomas Aquinas and scholasticism, which ground truth in God, appear in full.
Discover the courseFrequently asked questions
What are the transcendentals?
Properties that accompany every being: the one, the true, the good and the beautiful. They are being itself seen from different angles.
Are truth, goodness and beauty the same thing?
They are faces of one reality, being. They are distinguished by reason but imply one another: the true is intelligible, the good is desirable, and the union of the two, shining forth, is the beautiful.
Does this apply to ethics?
Yes. If the good is a transcendental, it corresponds to a truth about the human being, not to a taste. That is why there is a universal good, and not 'each to their own'.
Continue: What is truth · What is the Logos · What is alétheia
Source class (NousCast Community): The Idea of Truth (F&T 1.7)