"It is necessary to the happiness of man that he be mentally faithful to himself. Infidelity does not consist in believing, or in disbelieving, it consists in professing to believe what he does not believe"
About this Quote
The subtext is aimed at conformity as social technology. “Professing” is the key verb: it names belief as a civic ritual, a badge you wear to keep your job, your neighbors, your safety. Paine understood how institutions survive by turning inner life into a loyalty test. If you can be made to say what you don’t think, you can be made to do what you don’t want. Mental infidelity becomes political leverage.
It also flips the usual religious accusation. Orthodoxy often brands the dissenter as immoral; Paine brands the compliant hypocrite as the one corroding his own happiness. That’s shrewd rhetoric: he relocates virtue from correct doctrine to personal integrity, turning conscience into a kind of citizenship. The line lands because it’s both intimate and incendiary: it promises psychological relief (stop lying to yourself) while indicting an entire culture of forced consensus. In the age of revolutions, that’s not therapy. That’s strategy.
Quote Details
| Topic | Honesty & Integrity |
|---|---|
| Source | Thomas Paine, The Age of Reason (1794), Part I — contains the passage commonly printed as: "It is necessary to the happiness of man that he be mentally faithful to himself..." (found in standard editions and scanned archival copies). |
| Cite | Cite this Quote |
Citation Formats
APA Style (7th ed.)
Paine, Thomas. (n.d.). It is necessary to the happiness of man that he be mentally faithful to himself. Infidelity does not consist in believing, or in disbelieving, it consists in professing to believe what he does not believe. FixQuotes. https://fixquotes.com/quotes/it-is-necessary-to-the-happiness-of-man-that-he-23983/
Chicago Style
Paine, Thomas. "It is necessary to the happiness of man that he be mentally faithful to himself. Infidelity does not consist in believing, or in disbelieving, it consists in professing to believe what he does not believe." FixQuotes. Accessed February 1, 2026. https://fixquotes.com/quotes/it-is-necessary-to-the-happiness-of-man-that-he-23983/.
MLA Style (9th ed.)
"It is necessary to the happiness of man that he be mentally faithful to himself. Infidelity does not consist in believing, or in disbelieving, it consists in professing to believe what he does not believe." FixQuotes, https://fixquotes.com/quotes/it-is-necessary-to-the-happiness-of-man-that-he-23983/. Accessed 1 Feb. 2026.











