Commentaries:
Robertson's Word Pictures (NT)
But wilt thou know? (qeleiv de gnwnai). "But dost thou wish to know?" Ingressive aorist active infinitive of ginoskw (come to know). James here introduces a new argument like Romans 13:3.
O vain man (w anqrwpe kene). Goes on with the singular objector and demolishes him. For "empty" (deficient) Paul uses afrwn (fool) in I Corinthians 15:36 and just anqrwpe in Romans 2:1; Romans 9:20.
Barren (arge). See II Peter 1:8 (not idle nor unfruitful) and Matthew 12:36, but Hort urges "inactive" as the idea here, like money with no interest and land with no crops.
Other Robertson's Word Pictures (NT) entries containing James 2:20:
James 4:5
2 Peter 1:8
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