“No mask like open truth to cover lies,
As to go naked is the best disguise.”

Not sure,  at this point, what point Mr Congreve is making here, but the mentally ill will try to overwhelm and confuse the a circumstances to reach their objective, that being superiority.  And the rare truism does emerge. The mentally healthy just want to safely reach their intended destination safely, health and happiness.

We hold this truth to be self evident. The laws of nature and of nature's God will eternally supersede evils such as lies. Naked to the world, being not cloaked by carnal man's unlawful delusions (lies = lies specifically and in general, socialism, Keynesian economics, etc.).