What does this quote mean?

“A liar will not be believed, even when he speaks the truth.”

Repeated deception damages credibility beyond the original lie: once listeners have learned to expect false alarms, even a later truthful warning can fail to restore belief in time.

Source note: Joseph Jacobs, The Fables of Aesop, “The Shepherd Boy and the Wolf,” Project Gutenberg #28. The wise man of the village gives the moral after the boy’s repeated false cries cause the villagers to ignore his real warning.

“All that glisters is not gold.”

Appearance can imitate value without possessing it, so the line encourages evidence and discernment before admiration or trust.

Source note: Act 2, Scene 7; the inscription warns against judging by outward appearance.

“All warfare is based on deception.”

Strategy depends partly on managing what an opponent believes about intentions, strength, timing, and position rather than revealing every fact directly.

Source note: The Art of War, Chapter I “Laying Plans,” Lionel Giles translation (1910).

“The devil can cite Scripture for his purpose.”

Even respected language can be quoted selectively, so a citation should be judged by context and purpose rather than authority alone.

Source note: The Merchant of Venice, Act 1, Scene 3.

“We must know the truth; and we must avoid error.”

James separates two intellectual duties—seeking truth and avoiding falsehood—to show that prioritizing one over the other can produce different habits of belief and inquiry.

Source note: The Will to Believe, essay “The Will to Believe”; Project Gutenberg #26659. James immediately argues that truth-seeking and error-avoidance are distinct laws rather than two phrasings of one command.

“Happy is the man who learns from the misfortunes of others.”

Other people’s failures can become instruction when we pay attention to consequences before repeating the same mistake ourselves.

Source note: Moral printed after “The Lion, the Fox, and the Ass”; the fox changes his conduct after observing the ass’s fate.