What is Faith

I like Charles Spurgeon's definition.

"What is faith? It is made up of three things - - Knowledge, belief, and trust.  Knowledge comes first.  'How shall they believe in him of whom they have not heart?'  I want to be informed of fact before I can possibly believe it.  'Faith cometh by hearing.'  We must first hear, in order that we may know what it is to be believed.

Faith begins with knowledge.

The mind goes on to believe that these things are true.  The soul believes that God is, and that He hears the cries of sincere hearts; that the gospel is from God; that justification by faith is the grand truth which God hath revealed in these last days by His Spirit more clearly than before.  Then the heart believes that Jesus is verily and in truth our God and Savior, the Redeemer of men, the Prophet, Priest, and King of His people.  All this is accepted as sure truth, not to be called in question.  

I pray that you may at once come to this.  Get firmly to believe that the 'blood of Jesus Christ, God's dear Son, cleanses us from all sin.;' that  His sacrifice is complete and fully accepted by God on man's behalf, so that he that believeth on Jesus is not condemned.  

Believe these truths as you believe any other statements; for the difference between common faith and saving faith lies mainly in the subjects upon which it is exercised.

So far you have made an advance toward faith; only one more ingredient is needed to complete it, which is trust.  Commit yourself to the merciful God; rest your hope on the gracious gospel; trust your soul on the dying and living Savior; wash away your sins in the atoning blood; accept His perfect righteousness, and all is well.  

Trust is the the lifeblood of faith; there is no saving faith without it.

Faith is not a blind thing; for faith begins with knowledge.

It is not a speculative thing; for faith believes facts of which it is sure.

It is not an unpractical, dreamy thing; for faith trusts, and stakes its destiny upon the truth of revelation.  

This is one way of describing what faith is."

Charles Spurgeon  "All of Grace"