Ginomai, 'has come,' that which, not having actually been in being before (i.e. in the world), now begins to be so. So the Word was (v. 1), but everything else 'began to be.' The world 'had its being,' 'began to be,' through Him (v. 10). He 'became flesh' (v. 14), ginomai. So 'grace and truth came into being.' I am not satisfied with 'subsists,' but 'came' gives the idea of coming into the world. No doubt they did so, but the word has not this force. They began to exist de facto down here. The verb is singular, and 'grace and truth' go together in the person of Christ. Nothing subsisted by the law, it was a rule given; but grace and truth actually commenced to be, not in God's mind of course, but in revelation and actual existence down here. But its so taking place supposes its continuance.