A man who lies to himself, and believes his own lies becomes unable to recognize truth, either in himself or in anyone else, and he ends up losing respect for himself and for others. When he has no respect for anyone, he can no longer love, and, in order to divert himself, having no love in him, he yields to his impulses, indulges in the lowest forms of pleasure, and behaves in the end like an animal. And it all comes from lying - lying to others and to yourself.
I believe it is an established maxim in morals that he who makes an assertion without knowing whether it is true or false, is guilty of falsehood; and the accidental truth of the assertion, does not justify or excuse him.
Our intelligence is imperfect, surely, and newly arisen; the ease with which it can be sweet-talked, overwhelmed, or subverted by other hardwired propensities - sometimes themselves disguised as the cool light of reason - is worrisome.
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.
...And these vicissitudes come best in youth;
For when they happen at a riper age,
People are apt to blame the Fates, forsooth,
And wonder Providence is not more sage.
Adversity is the first path to truth:
He who hath proved war, storm, or woman's rage,
Whether his winters be eighteen or eighty,
Has won experience which is deem'd so weighty.