Unlike some terms such as Trinity and theology, the Bible itself provides a clear and concise definition of faith. Hebrews 11:1 says, “Now faith is the assurance of things hoped for, the conviction of things not seen.” In other words, faith is a staking of our hearts and minds on a reality that is beyond us, both in time and comprehension. It is ahead of us (“hoped for”) and above us (“not seen”).
To guard us against failing to unpack the full meaning in this verse ourselves, the author of Hebrews makes his definition clear by filling the remaining 39 verses of chapter 11 with example after example of what this faith looks like when lived out. He does this to ensure that we understand that “assurance of things hoped for” and “conviction of things not seen” are not merely words. True faith cannot exist as only thoughts or feelings. Instead, it affects all of life, giving birth to works of obedience and endurance.
And it is important to remember that “things hoped for” and “things not seen” do not refer (at least in Christian faith) to things that are imagined or invisible. These phrases refer to those realities that we know of through the Word of God. Christian faith is inseparable from and unfounded apart from God’s Word. Thus Paul writes in Romans 10:17, “So faith comes from hearing, and hearing through the word of Christ.” John Calvin is likewise careful to emphasize,
There is a permanent relationship between faith and the Word. He could not separate one from the other any more than we could separate the rays from the sun from which they come. … The same Word is the basis whereby faith is supported and sustained; if it turns away from the Word, it falls. Therefore, take away the Word and no faith will then remain. (Institutes, 3.2.6)