In the Old Testament, the Hebrew means essentially steadfastness, cf. Exodus 17:12, where it is used to describe the strengthening of Moses' hands; hence it comes to mean faithfulness, whether of God towards man (Deuteronomy 32:4) or of man towards God (Psalm 118:30). As signifying man's attitude towards God it means trustfulness or fiducia. It would, however, be illogical to conclude that the word cannot, and does not, mean belief or faith in the Old Testament for it is clear that we cannot put trust in a person's promises without previously assenting to or believing in that person's claim to such confidence. Hence even if it could be proved that the Hebrew does not in itself contain the notion of belief, it must necessarily presuppose it. But that the word does itself contain the notion of belief is clear from the use of the radical, which in the causative conjugation, or Hiph'il, means "to believe", e.g. Genesis 15:6, and Deuteronomy 1:32, in which latter passage the two meanings — viz. of believing and of trusting — are combined. That the noun itself often means faith or belief, is clear from Habakkuk 2:4, where the context demands it. The witness of the Septuagint is decisive; they render the verb by pisteuo, and the noun by pistis; and here again the two factors, faith and trust, are connoted by the same term. But that even in classical Greek pisteuo was used to signify believe, is clear from Euripides (Helene, 710), logois d'emoisi pisteuson tade, and that pistis could mean "belief" is shown by the same dramatist's theon d'ouketi pistis arage (Medea, 414; cf. Hipp., 1007).
In the New Testament the meanings "to believe" and "belief", for pisteon and pistis, come to the fore; in Christ's speech, pistis frequently means "trust", but also "belief" (cf. Matthew 8:10). In Acts it is used objectively of the tenets of the Christians, but is often to be rendered "belief" (cf. 17:31; 20:21; 26:8). In Romans 14:23, it has the meaning of "conscience" — "all that is not of faith is sin" — but the Apostle repeatedly uses it in the sense of "belief" (cf. Romans 4 and Galatians 3). How necessary it is to point this out will be evident to all who are familiar with modern theological literature; thus, when a writer in the "Hibbert Journal", Oct., 1907, says, "From one end of the Scripture to the other, faith is trust and only trust", it is hard to see how he would explain 1 Corinthians 13:13, and Hebrews 11:1.
The truth is that many theological writers of the present day are given to very loose thinking, and in nothing is this so evident as in their treatment of faith. In the article just referred to we read: "Trust in God is faith, faith is belief, belief may mean creed, but creed is not equivalent to trust in God." A similar vagueness was especially noticeable in the "Do we believe?" controversy—one correspondent says—"We unbelievers, if we have lost faith, cling more closely to hope and — the greatest of these — charity" ("Do we believe?", p. 180, ed. W. L. Courtney, 1905). Non-Catholic writers have repudiated all idea of faith as an intellectual assent, and consequently they fail to realize that faith must necessarily result in a body of dogmatic beliefs. "How and by what influence", asks Harnack, "was the living faith transformed into the creed to be believed, the surrender to Christ into a philosophical Christology?"