This word has more force now than formerly. In AV it signifies no more than 'unbeliever.' It occurs in 2Co 6:15; 1Ti 5:8 (RV 'unbeliever' in both). So 'infidelity' in 2Es 7:44 is simply 'unbelief' (Lat. incredulitas).
The Greek word is pisto" -->???????, 'not believing,' and hence an 'unbeliever.' 2Co 6:15; 1Ti 5:8. The word is translated 'unbeliever' in Lu 12:46; 1Co 6:6; 14:23; 2Co 6:14; and 'unbelieving' in 1Co 7:14-15; Tit 1:15; Re 21:8. Thus the scriptural use of the term does not imply the denial of the truth of Christianity, as it is now commonly understood.