2 Corinthians 1:12-14
Paul’s Letters free of duplicity and dissimulation
12 For this is our boast: the testimony of our conscience, that we have conducted ourselves in the world, and especially in our dealings with you, with a sincere transparency that is from God, not in accordance with worldly cleverness but with the grace of God. 13 For we write to you nothing other than what you read and understand. I hope that you will come to understand fully, 14 as indeed you have understood us in part, that we will be your pride [and joy], just as you will be ours, on the Day of our Lord Jesus.
Paul’s Jewish opponents, the false apostles, rejected both the dire warnings of 1 Corinthians (3:12-17; 5:6-8; 10:1-22; 11:27-32) and the subsequent claim of the Letter of Tears, that the Corinthians had incurred the divine displeasure and that the apostle, like Moses before him, was 'standing in the breach'. All this, they alleged, was nothing but a sophisticated deception. Paul was employing the rhetorical arts, they alleged, in order to deceive and defraud the church. In response, the apostle has described the mortal danger that he faced in the Province of Asia, and his wonderful deliverance by ‘God who raises the dead’; and he has expressed his confidence that God will again deliver him, as the community help him through their prayers (1:8-11). He now anticipates his opponents’ further response: once again, they will say, he is employing the sophistic arts, piling deception upon deception. He can expect no help from God!
Ἡ γὰρ καύχησις ἡμῶν αὕτη ἐστίν, τὸ μαρτύριον τῆς συνειδήσεως ἡμῶν, ὅτι ἐν ἁπλότητι a καὶ εἰλικρινείᾳ τοῦ θεοῦ, [καὶ] b οὐκ ἐν σοφίᾳ σαρκικῇ c ἀλλ᾽ ἐν χάριτι θεοῦ, ἀνεστράφημεν ἐν τῷ κόσμῳ, περισσοτέρως δὲ πρὸς ὑμᾶς.
a ἁγιότητι is read by p46 א* A B C K P Ψ 0121 0243 33 81 365 630 1175 1739 1881 2464 co Clement of Alexandria Origen Didymus the Blind; ἁπλότητιis read by א2 D F G L 104 1241 1505 Majority Text lat sy. Both readings are therefore well attested, and ἁγιότης and ἁπλότης are easily confused. However, (1) the immediate context favors ἁπλότης: Paul insists that what he wrote was what they read and understood (1:13); he did not act with ‘worldly cleverness’, i.e. cunning and duplicity; (2) in these verses Paul portrays himself as the Corinthians’ benefactor. The term ἁπλότης appears again in 9:11-13, as he invites the Corinthians to become benefactors of the church of Judea, using language that echoes 1:11. Since ἁγιότης is not found elsewhere in the Pauline Corpus and is the more difficult reading,  the evidence is difficult to evaluate.
b καί is omitted by א A B C D F G K L P Ψ 81 104 365 1241 1505 Majority Text it Ambrosiaster; καί is read by p46 B 0121 0243 6 33 630 1175 1739 1881 2464 ar f vg sy.
c F G read σαρκινῇ for σαρκικῇ.
‘For this is our boast,  the testimony of our conscience,  that we have conducted ourselves  in the world, and especially in our dealings with you, with a sincere transparency  that is from God,  not with worldly  cleverness , but according to the grace of God.’
Paul now gives grounds (γάρ) for his confident hope that many will give thanks for the gracious divine gift of a second deliverance (v. 11). His hope of a further deliverance is grounded in his confidence that he has discharged his apostolic duty with complete integrity. Clearly he does not expect his remarks to go unchallenged, for he resorts to self-praise. Though Paul's boasting language (καύχησις) is very rare in the secular literature of the period,  the word group has about 80 instances in the LXX, where it is used both of arrogant self-praise and of justifiable pride and 'serene confidence' . The καυχ - word group has 64 instances in the NT, 58 of which are in the undisputed Pauline Corpus, with 29 in 2 Corinthians. Self-praise was permissible, under certain circumstances, in both the Jewish  and the Gentile, Greco-Roman cultures. Plutarch, having condemned self-praise in general, adds,
Yet in spite of all this there are times when the statesman might venture on self-glorification (περιαυτολογίας), as it is called, not for any personal glory or pleasure, but when the occasion and the matter in hand demand that the truth be told about himself, as it might about another—especially when by permitting himself to mention his good accomplishments and character he is enabled to achieve some similar good ... Indeed it is not as a reward or compensation for his merit that the statesman demands recognition and values it when accorded to his acts: he does so rather because the enjoyment of confidence and good repute affords means for further and yet nobler actions. 
Paul proudly calls to his defence the testimony of his συνείδησις (‘the inward faculty of distinguishing right and wrong’, 'conscience').  The συνείδησις, which is possessed by all human beings, is understood to function objectively, evaluating one’s behaviour according to one's ethical norms.  ‘Violation of the norms is attended by awareness of specific moral failure’.  Paul seems to have regarded the conscience as being experienced as a semi-autonomous faculty whose independence of testimony can be trusted;  cf. 2 Cor. 4:2; 5:11. His ethical norms, he believed, like those of his Corinthian converts were written in his heart by the Holy Spirit (cf. on 3:3). Danker comments, 'In these verses [2 Cor 1:12-14] Paul writes in the vein of a public benefactor... Numerous ancient monuments record of their honorees that during their tour of duty they behaved in a manner worthy of their city... His own conscience and the perceptiveness of his addressees are all the witness he needs'. 
Paul's boast, the testimony of his conscience, is that he has conducted himself in the world, and especially towards the Corinthians, ἐν ἁπλότητι καὶ εἰλικρινείᾳ τοῦ θεοῦ. The prepositional phrases clarify the principles by which Paul claims to have conducted himself in general, and in particular in his dealings with the Corinthians. In view of his quotation of Jer 9:23(24), 'Let the one who boasts (ὁ καυχώμενος) boast in the Lord', in 1 Cor 1:31 and again in the present letter (10:17), it seems best to understand τοῦ θεοῦ as an ablative:  ‘we have conducted ourselves ... with a sincere transparency that is from God’. The apostle has not acted deceitfully; rather, his actions have been sincere, open and transparent. This statement is then clarified further by means of a striking antithesis, [καὶ] οὐκ ἐν σοφίᾳ σαρκικῇ ἀλλ᾽ ἐν χάριτι θεοῦ. As A. E. Harvey points out, the expression ἐν σοφίᾳ σαρκικῇ (literally, 'with earthly wisdom') is 'highly paradoxical': 'in Greek, as in English, [wisdom] was a virtue that combined intelligence with sound judgement and moral integrity, indeed it was the very goal and achievement of philosophy. In the Jewish tradition, likewise, it was God's gift to the greatest sages and was an aspect of God's creative power, the source of order and regularity in the universe'. 
The expression ἐν σοφίᾳ σαρκικῇ is contrasted explicitly (ἀλλʼ) with ἐν χάριτι θεοῦ, language which echoes the χάρισμα of v. 11. Just as Paul is now depending on God's grace for a second deliverance, so his recent conduct was guided by (a reliance upon) the grace of God. A contrast is also implied between conduct ἐν σοφίᾳ σαρκικῇ and conduct ἐν ἁπλότητι καὶ εἰλικρινείᾳ τοῦ θεου: had he acted in accordance with 'earthly wisdom', Paul implies, his conduct would have been neither sincere nor transparent. Similar expressions, also with negative nuances, occur in 1 Corinthians, with reference to the employment of the rhetorical arts: ἐν σοφίᾳ λόγου ('with manipulative rhetoric' ; 'with cleverness in speaking' ), 1:17; καθʼ ὑπεροχὴν λόγου ἢ σοφίας ('as a superior person in speech or [human] wisdom' ), 2:1; ἐν πειθοῖς σοφίας λόγοις ('with enticing clever words' ), 2:4 ; ἐν σοφία ἀνθρώπων ('by human wisdom'), 2:5; ἐν διδακτοῖς ἀνθρωπίνης σοφίας ('in speech taught out of mere human cleverness' ), 2:13. In 1 Cor 1:10-4:21, Paul goes out of his way to demonstrate his rhetorical skills,  and he clearly employs his brilliant mind to the full in the composition of his letters; he does not condemn eloquence or human wisdom per se. In view of his reference in v. 13 to what he writes, it is clear that Paul is defending the charge that in his letters he makes use of the rhetorical arts in order to deceive. In his handling of the recent crisis, he replies, he did not depend on his own cleverness, but on God's grace.
οὐ γὰρ ἄλλα γράφομεν ὑμῖν ἀλλ᾽ ἢ ἃ a ἀναγινώσκετε
a F G omit ἀλλ᾽; p46 33 945 1505 sy omit ἢ; D* 0243 1739 omit ἃ; A omits ἢ ἃ.
In the recent crisis Paul dealt with the Corinthians primarily through the Letter of Tears. He now clarifies (γάρ) his boast, that he has never resorted to duplicity and dissimulation in his dealings with the church. His letters have not misled them in any way: what he writes, they read (ἀναγινώσκω) and understand (ἐπιγινώσκω). The paronomasia underscores the point: his letters, and the Letter of Tears in particular, say what he means, and what they have read and understood is what he intended to say.
ἢ καὶ ἐπιγινώσκετε· a ἐλπίζω δὲ ὅτι ἕως τέλους ἐπιγνώσεσθε, 14 καθὼς καὶ ἐπέγνωτε ἡμᾶς ἀπὸ μέρους, ὅτι καύχημα ὑμῶν ἐσμεν καθάπερ καὶ ὑμεῖς ἡμῶν ἐν τῇ ἡμέρᾳ τοῦ κυρίου [ἡμῶν] b Ἰησοῦ.
a ἢ καὶ ἐπιγινώσκετε is omitted by p46 B 104 boms.
b ἡμῶν is omitted by p46vid A C D K L Ψ 1241 1505 Majority Text Ambrosiaster, and attested by א B F G P 0121 0243 6 33 81 104 365 630 1175 1739 1881 2464 lat syp.h** co. Though there is a scribal tendency to expand the divine names, 'our Lord Jesus' is not a customary liturgical formula. 
‘Now I hope that you will understand fully,  as  you have indeed understood us in part, that  we will be your pride (and joy), just as you will be ours, on the Day of our Lord Jesus.’
The Corinthians have indeed understood Paul in part. They have demonstrated this through their pleasingly vigorous response to the Letter of Tears (7:7-11). They have not understood him fully, however, for the accusations of his opponents have gained sufficient traction that he feels the need to answer them. Paul’s hope is that the church will now come to understand him fully – that they will understand that he will be their ground of boasting (καύχημα), just as they will be his, on the Day of our Lord Jesus  - that is, when they are presented together to the Court of Heaven at the Parousia (4:14).
The expressions ἀπὸ μέρους and ἕως τέλους can, however, mean respectively ‘for a while’  and ‘until the end’, and in view of his reference to the eschatological judgment, Paul certainly expresses the hope that the Corinthians will understand him fully on that Day. Furthermore, Paul almost certainly perceived a danger that the Corinthians would lose their grip on the partial understanding that they did have (cf. 11:2-4). The alternative senses are so closely interrelated that the ambiguity may be intentional.
Verses 12-14 are marked as a paragraph by inclusion (καύχησις … καύχημα). Given the conventions of ancient rhetoric, with which Paul’s original readers will have been fully familiar, the position of vv. 12-14, following his Benediction and the narrative of 1:8-11, creates the impression that Paul is launching into a forensic speech - a defence of his conduct, and that in these verses he is setting out the theme statement of his letter. Though this does not in fact turn out to be the case, Paul does here signal his intention to answer fully the charges of his opponents in relation to the Letter of Tears, and in fact he undertakes this task in 1:15-5:10. In so doing he builds upon what his addresses have understood already from his letters, so providing them with a basis for boasting in him before his opponents (5:12), and for taking pride in him at the Parousia.
 The pronoun αὕτη is the subject nominative; ̔Η γὰρ καύχησις ἡμῶν is the predicate, which is then expanded by apposition with τὸ μαρτύριον τῆς συνειδήσεως ἡμῶν, and then by the ὅτι clause, which gives the content of Paul’s testimony.
 An attempt to render the hendiadys ἐν ἁπλότητι καὶ εἰλικρινείᾳ. BDAG s.v. ἁπλότης, ‘personal integrity expressed in word or action (cp. our colloq. “what you see is what you get”)’; s.v. εἰλικρινεία, ‘the quality or state of being free of dissimulation’.
 Taking τοῦ θεοῦ to be ablative.
 ' Thesaurus Linguae Graece 3.1 notes καυχη- 69 times until the end of the first century CE (most of them in the sixth and fifth century BCE) ... In the first century, καυχη- occurs three times in Philo, three in Josephus, two in Plutarch, one in Apollonius the Sophist'; Wojciechowski, Paul and Plutarch on Boasting 101 n 15. The word group is found in the documentary papyri (MM).
 'It is permitted to humans to find glory in the divine works and in their piety (1 Chron. 16.28-29; 29.11; Pss 5.11; 89.15-18; Sir. 1.11; 9.16; 10.22; 17.9; 39.8; 50.20)'; Wojciechowski, Paul and Plutarch on Boasting 99-100.
 I owe this insight to Professor Carl W. Conrad.
 The clause καθὼς καὶ ἐπέγνωτε ἡμᾶς ἀπὸ μέρους is parenthetical; the following ὅτι clause is taken to be the object of ἐπιγνώσεσθε.
 For the expression ἡ ἡμέρα τοῦ κυρίου, ‘the Day of the Lord’, cf. 1 Cor 1:8; 5:5; Phil 1:6, 10; 2:16; 1 Thess 5:2; 2 Thess 2:2.