εἰλικρινής

From the study of 2 Peter 3:1

Range of meaning

Unmixed, unadulterated, pure in substance; then, of people and thoughts, sincere, without hidden motive, transparent. Ancient writers already guessed at where the word came from: "tested by sunlight" (heilē, sunlight, plus krinō, judge), like cloth held up to the light to check for flaws. Another guess is "sifted" (from heileō, to roll or whirl). Both are uncertain, but the meaning in actual use is clear: free of mixture or contamination (BDAG; LSJ).

Against the English

KJV/YLT "pure"; WEB, ESV, NASB "sincere"; BSB, NIV and NLT render the phrase "wholesome thinking." "Pure" is a true gloss, but modern English hears it as moral or sexual purity. "Sincere" now means "heartfelt, not faking" and loses the sense of "unmixed."

How it drifted

In English, "pure mind" has come to mean mostly a mind free of lustful thoughts (compare "pure thoughts" in devotional language). The Greek word is about being unmixed: thinking not diluted or contaminated by something foreign.

Used elsewhere in the period

Plato, Phaedo 66a uses almost the same phrase, εἰλικρινεῖ τῇ διανοίᾳ ("with pure, unmixed thought"), for reason working without the distortion of bodily senses. In Wisdom 7:25 Wisdom is "a pure emanation" of God's glory. Paul uses the word in Phil 1:10 ("pure and blameless") and the related noun in 1 Cor 5:8 and 2 Cor 1:12, 2:17, where he sets sincerity against those who "peddle" (water down) God's word.

From the study of Philippians 1:10

Range of meaning

Unmixed, unalloyed, pure of any foreign substance; by extension, morally pure and transparent in motive, without hidden agendas.

Against the English

KJV/WEB/NASB 'sincere' comes through the Vulgate's sinceri. Modern 'sincere' means 'genuinely meaning what you say or feel', which is narrower than the Greek. 'Pure' (BSB, NIV, ESV) is closer.

How it drifted

English 'sincere' has narrowed to emotional genuineness. A person can be 'sincere' and still be badly mixed in motive, while eilikrinēs is precisely about nothing being mixed in.

Used elsewhere in the period

Plato, Phaedo 66a, uses it for pure, unmixed thought. Wisdom of Solomon 7:25 calls Wisdom 'a pure emanation (eilikrinēs) of the glory of the Almighty'. Paul uses the noun eilikrineia in 1 Cor 5:8 (unleavened bread of purity, contrasted with old leaven) and 2 Cor 2:17 (contrasted with those who 'peddle', i.e. water down, the word). 2 Pet 3:1 has 'your pure mind'. An ancient explanation derives it from heilē/hēlios ('sunlight') + krinō ('judge'), meaning 'tested in sunlight', but this etymology is uncertain.