I lay it down as a foundation principle, which no one can gainsay, that of course [God's] voice will always be in harmony with itself, no matter in how many different ways he may speak. The voices may be many, the message can be but one, if God tells me in one voice to do or to leave undone anything he cannot possibly tell me the opposite in another voice. If there is a contradiction in the voices, the speakers cannot be the same. Therefore my rule for distinguishing the voice of God would be to bring it to the test of this harmony.