Ephesians 1:3-14 contains a number of "thorny" interpretative issues. A particularly significant problem is the meaning and translation of the infinitive anakephalaiwsasthai in 1:10b. Given that this phrase expresses a central part of the author's (Paul?) argument (scholars suggest 1:9-10 is the focal point of the passage), interpretative precision on this issue is critical to understanding this passage. Here is Max Turner's ("Mission and Meaning in Terms of 'Unity' in Ephesians" in Mission and Meaning: Essays Presented to Peter Cotterell) assessment:
"The translation of the verb anakephalaioo as "to bring back into unity" requires some brief justification. While the NIV follows an exegetical tradition that takes the verb to mean 'bring under one head', this should probably be rejected because it would suggest (incorrectly) that the verb derives from the noun kephale ('head') rather than from kephalaion ('main point', 'summary'). Etymology would thus rather support the sense 'to sum up' (as in Rom. 13:9) or possibly 'to recapitulate' (if weight is given to the prefix) . . . the phrase 'all things . . . the things in the heavens and the things on earth in him' strongly evokes the centre-piece hymnic passage of the sister letter, Colossians (1:15-20). The latter asserts that all things 'in the heavens and on the earth' were initially created in Christ (1:16), and that through the death and resurrection-exaltation of Christ 'all things' 'whether on earth or in the heavens' would eventually once more become reconciled (i.e. brought back from warring alienation into peaceful unity under God). The Colossians parallel thus suggests that the 'summing up' of all things in Christ envisaged in Ephesians 1:10 is God's bringing of them back into harmonious unity in and through Christ" (139-140).
Turner's essay also has some helpful comments on the relationship between Eph 1-3 and 4-6. Especially interesting is his discussion of the author's "new creation" theology, a motif that is implicit in Eph 1:10 and finds expression throughout the letter (cf. 2:1-10; 4:17-24).