Joshua said, Hereby you shall know that the living God is among you, and that he will without fail drive out from before you the Canaanite, and the Hittite, and the Hivite, and the Perizzite, and the Girgashite, and the Amorite, and the Jebusite.
When Joshua says that the people will know the presence of God from the miracle, he indirectly upbraids them with their distrust, as the mere promise of God ought to have sufficed for a full assurance, and our faith, unless founded solely on this promise, must be continually wavering. But although faith ought properly to recline on the truth of God alone, it does not follow that experimental knowledge may not act as a secondary support to its weakness, and give subsidiary aid to its confirmation. For that which God promises to us in word he seals by act, and as often as he exhibits to us manifestations of his grace and might, he intends them to be so many confirmations of what he has spoken, and so many helps tending to suppress all our doubts. 