Imagination does not, in its own nature, involve any certainty of truth, such as is implied in every clear and distinct idea, but requires some extrinsic reason to assure us of its objective reality: hence prophecy cannot afford certainty, and the prophets were assured of God's revelation by some sign, and not by the fact of revelation, as we may see from Abraham, who, when he had heard the promise of God, demanded a sign, not because he did not believe in God but because he wished to be sure that it was God Who made the promise. The fact is still more evident in the case of Gideon: "Show me," he says to God, "show me a sign, that I may know that it is Thou that talkest with me." God also says to Moses: "And let this be a sign that I have sent thee." Hezekiah, though he had long known Isaiah to be a prophet, none the less demanded a sign of the cure which he predicted. It is thus quite evident that the prophets always received some sign to certify them of their prophetic imaginings; and for this reason Moses bids the Jews (Deut. xviii.) ask of the prophets a sign, namely, the prediction of some coming event. In this respect, prophetic knowledge is inferior to natural knowledge, which needs no sign, and in itself implies certitude. Moreover, Scripture warrants the statement that the certitude of the prophets was not mathematical, but moral. Moses lays down the punishment of death for the prophet who preaches new gods, even though he confirm his doctrine by signs and wonders (Deut. xiii.); "For," he says, "the Lord also worketh signs and wonders to try His people." And Jesus Christ warns His disciples of the same thing (Matt. xxiv. 24). Furthermore, Ezekiel (xiv. 9) plainly states that God sometimes deceives men with false revelations; and Micaiah bears like witness in the case of the prophets of Ahab. Although these instances go to prove that revelation is open to doubt, it nevertheless contains, as we have said, a considerable element of certainty, for God never deceives the good, nor His chosen, but (according to the ancient proverb and as appears in the history of Abigail and her speech), God uses the good as instruments of goodness, and the wicked as means to execute His wrath. This may be seen from the cases of Micaiah above quoted; for although God had determined to deceive Ahab, through prophets, He made use of lying prophets; to the good prophet He revealed the truth, and did not forbid his proclaiming it. Still the certitude of prophecy remains, as I have said, merely moral; for no one can justify himself before God, nor boast that he is an instrument for God's goodness. Scripture itself teaches and shows that God led away David to number the people, though it bears ample witness to David's piety. The whole question of the certitude of prophecy was based on these three considerations:-- 1. That the things revealed were imagined very vividly, affecting the prophets in the same way as things seen when awake;