As I've noted before, the unity of truth, good, and beauty is close to the heart of the Socratic-Platonic-Aristotelian tradition. That's because the highest thing we can know or understand is not the world or even ourselves, but the good. Socrates realized this when he turned away from natural philosophy to the consideration of human affairs. For Aristotle, an understanding of the human good is the key to avoiding the extremes of foolishness and cunning, and thus achieving wisdom or φρόνησις; and an understanding of the divine (the good in its purest form) is the key to avoiding the extremes of ignorance and sophistry or deception, and thus achieving sagacity or σοφία.
This implies that epistemology is inherently ethical - that you need to be good in order to correctly and fully understand why things are the way they are. Indeed, it seems to me that all of the virtues apply not only to action but also to inquiry (for inquiry too is a form of activity). Thus in order to come at all close to wisdom or sagacity, you must have the intellectual courage to pursue truth wherever it may lead, the intellectual moderation or temperance to steer clear of partisanship, the intellectual generosity to give freely of your own insights, the intellectual mildness or gentleness to not get angry in the face of disagreement, the intellectual honesty to admit or even ferret out when and why you are wrong, the intellectual benevolence to care about other people's thoughts and conclusions, the intellectual compassion to see the world from other people's perspectives, the intellectual dignity to not manipulate people into agreeing with you, the intellectual justice or fairness to accurately represent other points of view, and so on. Thus truth and goodness are tightly intertwined.
What of goodness and beauty? For Aristotle, excellence of character had to be founded in a steadfast commitment to what is beautifully right or καλός - a phenomenon that straddles the fence between the ethical and the aesthetic. The best, most beautiful actions and feelings have a rightness about them, they are proportional to the situation you find yourself in, they fit seamlessly together, they don't leave out anything important, they are well ordered, they bespeak a certain personal stature, and they are significant and meaningful to the people involved. These nominally aesthetic qualities are all in play when we say to someone, "That was a beautiful thing you did."
Although Plato and Aristotle didn't draw out all the implications of these connections in their writings, they might have done so in their philosophical communities (the Academy and Lyceum), which you likely couldn't have joined unless you were already a good person. And, following Socrates, they firmly held that the love of wisdom and the pursuit of truth were best done with people you care about and who care about you. Ultimately this means that truth and goodness and beauty are not merely abstract ideas but intimately and irreducibly personal. Thus what has seemed faraway all these millennia might be much nearer than we ever thought possible.
(Cross-posted at philosopher.coach.)
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