All significant truths are private truths. As they become public they cease to become truths; they become facts, or at best, part of the public character; or at worst, catchwords.
The solar system has no anxiety about its reputation, and the credit of truth and honesty is as safe; nor have I any fear that a skeptical bias can be given by leaning hard on the sides of fate, of practical power, or of trade, which the doctrine of Faith cannot down-weigh.
Even as wisdom often comes from the mouths of babes, so does it often come from the mouths of old people. The golden rule is to test everything in the light of reason and experience, no matter from where it comes.
Since an intelligence common to us all makes things known to us and formulates them in our minds, honorable actions are ascribed by us to virtue, and dishonorable actions to vice; and only a madman would conclude that these judgments are matters of opinion, and not fixed by nature.