Many Protestants today realize that Catholics adhere to two of the important "solas" related to salvation sola gratia (by grace alone) and solo Christo (by Christ alone) but fewer are aware that Catholics can also accept the formula of justification sola fide (by faith alone), provided this phrase is properly understood. The term pistis is used in the Bible in a number of different senses, ranging from intellectual belief (Romans 14:22, 23, James 2:19), to assurance (Acts 17:31), and even to trustworthiness or reliability (Romans 3:3, Titus 2:10). Of key importance is Galatians 5:6, which refers to faith working...