Emily Dickinson Lexicon

argument (-s), n. [see argue, v.] (webplay: arch, first, unknown).

1. Copious phrase; profuse expression; [fig.] eloquence; silver-tongued melody.
2. Evidence; deposition; proof; statement; testimony; witness; [fig.] shining; silvery light; [NW] “In astronomy, an arch by which we seek another unknown arch.”