In his early years, John Wesley was heavily influenced by the English philosopher, John Locke. This influence is evident in a letter he wrote to his mother. “I call faith an assent upon rational grounds; because I hold Divine testimony to be the most reasonable of all evidence whatever. Faith must necessarily, at length, be resolved into reason.”
His mother, Suzanna, responded to Wesley in what I think is one of the clearest descriptions of faith, “You are somewhat mistaken in your notions of faith. All faith is an assent, but all assent is not faith. Some truths are self-evident, and we assent to them because they are so. Others, after a regular and formal process of reason by way of deduction from some self evident principle, gain our assent. This is not properly faith but science. Some again we assent to, not because they are self-evident, or because we have attained the knowledge of them in a regular method by a train of arguments; but because they have been revealed to us, either by God or man, and these are the proper objects of faith. The true measure of faith is the authority of the revealer, the weight of which always holds proportion to our conviction of his ability and integrity.”