Faith answers the question, 'How?' with one word: 'God!' The Bible says, 'Faith is the substance of things hoped for, the evidence of things not seen.' (Hebrews 11:1 NKJV) Notice:

(1) Faith is a 'substance'.

Some people see faith as something ethereal and 'otherworldly'. But it's not; we use faith every day. For example, you pick up the phone, call a department store, place an order, and they ask for your credit card number. Then they give you a receipt number. The receipt is what you hold on to while you're waiting for the item to arrive - it gives you the assurance that the product is on the way. And the same is true in the spiritual realm. God promises to answer your prayer, you believe Him, but your faith is the 'substance' or the receipt you hold on to while you're waiting.

(2) Faith is also 'evidence.'

Why would you believe that someone you can't see on the other end of a phone line would send you something just because you order it? Because it happens every day for others, and it's probably happened to you before. Therefore you're not being presumptuous or silly when you go to your letterbox expecting it to be there. You are not the first person to trust God and you won't be the last. 'Lord, You have been our dwelling place in all generations.' (Psalm 90:1 NAS) People have been trusting God for thousands of years and He has never let them down. His faithfulness is all the 'evidence' you need. So it's not foolish to put your trust in a God like that, is it?