Seem ( δοκεῖ); seems to himself rather than to others; translate, with R.V., thinketh himself to be. Vulgate, Si quis Putat se esse. Religious ( θρῆσκος). It is difficult to find an English word which exactly answers to the Greek.
The noun θρησκεία refers properly to the external rites of religion, and so gets to signify an over-scrupulous devotion to external forms (Lightfoot on Colossians 2:18); almost "ritualism." It is the ceremonial service of religion, the external forms, a body of which εὐσεβεία is the informing soul.
Thus the θρῆσκος (the word apparently only occurs here in the whole range of Greek literature) is the diligent performer of Divine offices, of the outward service of God, but not necessarily anything more.
This depreciatory sense of θρησκεία is well seen in a passage of Philo ('Quod Det. Pot. 'Jus.,' 7), where, after speaking of some who would fain be counted among the εὐλαβεῖς on the score of diverse washings or costly offerings to the temple, he proceeds: πεπλάνηται γὰρ καὶ οὖτος τῆς πρὸς εὐσεβείαν ὁδοῦ θρησκείαν ἀντὶ ὁσιότητος ἡγούμενος (see Trench on 'Synonyms,' from whom the reference is here taken).
"How delicate and fine, then, St. James's choice of θρῆσκος and θρησκεία! 'If any man,' he would say, 'seem to himself to be θρῆσκος, a diligent observer of the offices of religion, if any man would render a pure and undefiled θρησκεία to God, let him know that this consists, not in outward lustrations or ceremonial observances; nay, that there is a better θρησκεία than thousands of rams and rivers of oil, namely, to do justly and to love mercy, and to walk humbly with his God (Micah 6:7, Micah 6:8); or, according to his own words, ' to visit the widows and orphans in their affliction, and to keep himself unspotted from the world'".
Bridleth not ( μὴ χαλιναγωγῶν). The thought is developed more fully afterwards (see James 3:2, etc., and for the word, cf. Polyc., 'Ad Philippians,' c.v).