Many things are accepted and acted upon by faith. Before we were born, the pyramids of Egypt were built. We were not present at that time so we have no immediate knowledge of it, yet, we believe that intelligent beings erected them because they show evidence of intelligent design and construction. Using that same logic in the spiritual realm brings us to similar conclusions.
Before we were born the universe was created by God. We were not present at that time so we have no immediate knowledge of it, yet, we believe that an intelligent being created it because it shows evidence of intelligent design and construction. That intelligent being is the God who reveals Himself in the Bible. As we come to know Him, His character, power and wisdom, we have faith in Him that He is able to do all He promises. Ephesians 3:20, in speaking of God, says, "Now to Him who is able to do exceedingly abundantly above all that we ask or think, according to the power that works in us." Romans 4:21 says that the great Old Testament patriarch Abraham was "fully convinced that what He had promised He was also able to perform."
The evidence of one's faith in God is obedience to His will. James 2:17 states, "Thus also faith by itself, if it does not have works, is dead" (cf. Jas. 2:20, 24). Faith enables one to obey in the absence of understanding the why and how of the thing commanded. Faith is a trust that assures one that he will receive a promise, though the means of fulfillment is not obvious because he has confidence in the one who revealed it. The evidence of faith is seen in the actions of the faithful as seen in the eleventh chapter of Hebrews.
The cleansing or purifying of the heart. The apostle Peter, in reference to the Gentiles and how they were acceptable to God without being circumcised, said, "Men and brethren, you know that a good while ago God chose among us, that by my mouth the Gentiles should hear the word of the gospel and believe. So God, who knows the heart, acknowledged them by giving them the Holy Spirit, just as He did to us, and made no distinction between us and them, purifying their hearts by faith" (Acts 15:7-9).
Justification before God. "Therefore, having been justified by faith, we have peace with God through our Lord Jesus Christ" (Rom. 5:1; cf. Rom. 3:28).
Salvation. "For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast" (Eph. 2:8-9).
Great boldness and confidence. Addressing the church at Corinth, the apostle Paul said, "Not that we have dominion over your faith, but are fellow workers for your joy, for by faith you stand" (2 Cor. 1:24).
Life. Romans 1:17, in speaking of the gospel, says, "For in it the righteousness of God is revealed from faith to faith; as it is written, 'The just shall live by faith'" (cf. Gal. 2:20, 3:11).
Protection from the evil one. As part of the "whole armor of God," the believer takes up "the shield of faith with which you will be able to quench all the fiery darts of the wicked one" (Eph. 6:16).
Triumph. "And this is the victory that has overcome the world -- our faith" (1 John 5:4).