What is "saving truth"and "healing grace"?
The original sentence is from the marks of an educated man. "Any education that matters is liberal. All the saving truths and healing graces that distinguish a good education from a bad one or a full education from a half-empty one are contained in that word"

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In this context, it simply means the distinguishing points, or markers, of a good education. The phrases are both common cultural references to Christianity. "The saving truth of the gospels" and "The healing graces of the Lord."