Hebrews 11:1

Both nouns in this definition are legal and commercial, not emotional.

Assurance translates a word used in contemporary documents for a title deed — the paper establishing that something is yours before you have taken possession of it. Proof is the word for evidence that would be accepted in court.

So faith, in this definition, is not a feeling of confidence. It is the documentation. And the two objects tell you why documentation is needed: things hoped for, which have not arrived, and things not seen, which cannot be inspected. Both are cases where possession and evidence have come apart.

What follows in the chapter is the argument for the definition, and it is unsparing. The list of people who lived this way includes some who saw the promise fulfilled and many who did not. Verse thirteen says plainly that these all died in faith, not having received the promises, but having seen them and greeted them from afar.

And near the end the writer lists those who were tortured, sawn apart, and wandered in deserts — of whom the world was not worthy — and says they did not receive the promise either.

Which means the chapter is not offering faith as a technique for obtaining things. It is describing how people hold a title deed for a lifetime without ever seeing the property.