To recover the word sincerity from its current mangled form, we might remember some etymology. The etymology of sincerity is a favorite among preachers, and for good reason – it’s an interesting tale. It seems in the Graeco-Roman world, unscrupulous merchants had found a nifty way to sell otherwise useless cracked pottery. By using wax, which could be colored to match the pottery, small or larger cracks in the clay could be concealed. Not repaired, mind you, merely concealed – for when the Mediterranean sun did its work, the wax in those pots would soften or even melt, and the pottery could collapse and lose its contents. Like the used car rigged to last just one test drive, pots with wax could impress while on the shelf, but not endure real-life use. At some point, merchants decided to offer a guarantee of sorts: in Latin, sine cera: “without wax”. The “sincere” pottery was simply the real deal, not hiding flaws that would render it useless.
While etymology doesn’t determine the meaning of words, the proper meaning of sincere is not far from its root. A sincere man is one without pretense, without deception. Sincerity is very close to what the Bible calls integrity: wholeness, consistency. A man with integrity does not have a private life which contradicts his public claims. His character is not shot through with waxed over fatal flaws. A sincere man is a man with integrity, who seeks to be as much on the inside what he is on the outside.
Sincerity has nothing to do with formality or informality. One can be completely sincere and observe custom, ritual, or manners. Conversely, one could throw off all formality, be as casual as a surfer on Sunday, but remain a hypocrite, having different faces for different places.
Sincerity also has nothing to do with how public you make your inner or private world. Many of our private moments should remain just so. Instead of supporting the weird exhibitionism and voyeurism that much social media encourages in all of us, we should foster a healthy privacy, without cultivating an unhealthy secrecy. Sincerity is not making a public confession where none was asked for, venting your frustration because you want to be “open and honest”, or expecting some kind of therapeutic listen-‘n-share group in the church.
Sincerity has nothing to do with how sensate your feelings are to you. While worship must come from a sincere heart (1 Timothy 1:5, Matthew 6:1-18, 15:8), that really has nothing to do with how intensely you feel your feelings in worship. On a given Lord’s Day, your physical condition, relative mental sharpness, or overall spiritual maturity may render your sense of your own affections less acute. That does not mean the worship was offered insincerely, or with the aim of impressing others, or to mask some monstrous sin.
Sincerity has nothing to do with how relaxed, casual, and familiar you feel. You may feel quite tense, nervous, or awkward, and be entirely sincere. Indeed, in circumstances or occasions of great moment, we would expect both sincerity and carefulness. It’s true that awkwardness can tempt men to posture and act seriously, so as to fit in. It’s equally true that casualness can tempt men to be flippant and profane so as to fit in.
Sincerity has everything to do with truth. The sincere man wants the truth of reality, so he does not immerse himself in amusement. He wants truth in his words, so he learns to say what he means and mean what he says. He wants truth about God and man rightly symbolized, so he does not fear custom, tradition, or formality, but can penetrate their meaning and use them sincerely. He wants truth about himself, so he is able to acknowledge his failures, even among other believers (James 5:16), without polluting the minds of others with graphic descriptions of his every sin (Eph 5:12). He wants truth in his own affections, so he works on chastening and training his affections to love what he ought to love, in the way he ought to love it (Phil 1:9-11), and not giving place to every emotion that emanates from his heart.
In short, the sincere man is wrestling against the deceptiveness of his own nature, fighting man-pleasing, pride, hypocrisy, and narcissism. The very last thing he needs is to become intensely self-conscious of just how sincere he is (compared to all those fake, phony people out there, you know). That’s like becoming proud of your achievements in humility.
Instead, he prays David’s prayer for truth in the innermost man (Ps 51:6). He repents of eyeservice. He seeks to love men, not please them. He does not “really want sincerity” as much as he sincerely wants reality.