It is dangerous to take any sentence in isolation and consider it bereft of context, for that is how meaning and intent get distorted, but noteworthy in this sentence even in isolation from Paul's Letter to the Hebrews is the complete absence of any reference to God. Even the sentence that follows this refers to men, and not to God: "This is what the ancients were commended for."
To the obvious rebuttal that the Apostle Paul is speaking specifically about faith in God throughout the Epistle and thus there is no need to mention of God in this sentence, there is the counter that if Paul addresses a specific form of faith, it follows there must then be a general--generic--concept of faith. This general formulation of faith is what Paul gives us at the beginning of Chapter 11 of his Letter to the Hebrews. As Paul gives us a general formulation of faith, we may safely extract it from the surrounding text without doing violence to that text, and explore the nature of faith.
Faith Is "Knowledge" Without Evidence
Faith is an assurance about what we do not see. Faith is a realization that there is knowledge and reality beyond what we have already seen and experienced--we "know" there is "something" more without having the empirical experience of that something within our five senses.
Yet faith is more crucial, more essential, than this, for if knowledge comes to us through our five senses, something besides knowledge must impel us to see, to sense, to experience, and to thus gain that knowledge. Knowledge may perhaps guide us to new knowledge, but it cannot be the motivator for that quest; the effect can never be its own cause.
Thus even the most rational of scientists depends on the excellence of his faith, for it is that faith in yet-unknown knowledge that is the invisible hand behind every experiment, and all research. Properly apprehended, not only is there no conflict between faith and science--between faith and reason--but there is a clear intertwining of the two; reason cannot begin without faith, and rewards faith with new knowledge and new learning.
Faith Is Trust
Faith is a confidence in what we hope for. Faith is a trust that what we wish to be will be. Faith, in addition to motivating us to see and to sense, reassures us the effort will not be wasted. How could there be any motivation to labor in a laboratory, or to explore, or even to sit in a classroom listening to lectures, if there was not the presumption--the belief--that the knowledge we sought was in some way "knowable"?
Without that presumption, without that belief, the effort made to see, to sense, and to learn would be crippled by an overwhelming futility. Faith impels us to step forward, and reassures us there is solid ground awaiting our feet.
Faith is therefore not merely the complement of reason, it is its predicate. Faith is an absolute necessity; we are not able to avoid faith, to evade belief of one form or another. Without faith, we are neither inspired to step forward nor assured that in stepping we will not fall. Without faith, we would not--we could not--step forward.
Without faith, we cannot learn. Without faith, we cannot act. Without faith, we cannot grow.
Do. Or Do Not.
In the movie Star Wars: The Empire Strikes Back, the hero Luke Skywalker is challenged by his mentor Yoda to lift his fighter craft out of a swamp with just the power of his mind. Luke's doubtful mumbling of "I'll give it a try" is met with Yoda's sharp rebuke "Try not. Do. Or do not. There is no try." Chastened, Luke makes the attempt....and fails. Whereupon Yoda effortlessly lifts the vehicle out of the mud and guides it to dry land.
When Luke expresses his amazement, saying "I don't believe it," Yoda gently rebukes him further, pointing out "that is why you fail." Knowledge and skill were insufficient for Luke to surmount the challenge; lacking confidence in what he hoped for (salvaging his fighter craft), he was unable to obtain that which he hoped for. Lacking faith, he failed.
This is not a new idea. Even the malevolent Lady Macbeth counseled to "screw your courage to the sticking point, and we'll not fail" (coming as it did in Shakespeare's play as an exhortation to murder, this is an admittedly perverse depiction of the power of faith).
It is nevertheless an important idea. Whatever we would do, whatever we would learn, we must first believe in it. In order to act, we must first have faith. However we individually apprehend faith, faith is always the prime mover for everything we would do. Nothing can precede faith, and nothing can proceed without faith. Faith is as essential to daily living as is sleeping and eating.
Faith Is Unavoidable
With each new day, we must face new challenges; they are already there, we cannot avoid them. With each new day, we must answer new questions; they are already there, we cannot avoid them.
Whichever way we turn, there are challenges, and there are questions. Life itself demands that we meet these challenges, and answer the questions.
Faith allows us to meet these challenges. Faith is how we answer all the questions.
With faith, through faith, by faith--thus we begin.