The system of philosophy set forth in the poem is now to be considered. Few persons could have been less qualified than Bolingbroke and Pope to write on natural religion. The desultory superficial investigations of Bolingbroke were under the dominion of his passions, and Pope had barely thought upon the subject at all. They both took for their motto a sentence from Foster, a dissenting minister,--"Where mystery begins religion ends,"[805]--and it did not occur to them that no mystery could be greater than the first article of their own deistical creed,--the necessary existence of God. Atheism magnifies the mystery, which is an inherent ingredient in every system, religious or infidel. The least reflection forces this fact upon the mind, and the blindness of Pope and Bolingbroke to a truth which met them at the threshold of their speculations, and recurred at every turn, is not an unjust measure of their general incapacity for religious philosophy. The Essay on Man was framed on the old and obvious division of ethics, which treated of man in his relation to God, his fellow-creatures, and himself. Pope, who thought it presumption to study God,[806] passed over the first of the three heads, and substituted an epistle on man in relation to the universe. The leading arguments in this opening epistle were taken from the Théodicée of Leibnitz, the Moralists of Shaftesbury, and the Origin of Evil, by Archbishop King. The poet had read the essay of Shaftesbury, and had possibly looked into King; but of Leibnitz he was entirely ignorant. In reply to the charge of having adopted the alleged fatalism of the illustrious German, he wrote to Warburton, Feb. 2, 1739, "It cannot be unpleasant to you to know that I never in my life read a line of Leibnitz, nor understood there was such a term as pre-established harmony till I found it in M. Crousaz's book." Bolingbroke had instructed Pope that Leibnitz was "one of the vainest and most chimerical men that ever got a name in philosophy, and that he was so often unintelligible that no man ought to believe he understood himself."[807] Naturally Pope had not the least suspicion that some of the principal tenets instilled into him by his "guide" were filched without acknowledgment from this vain, chimerical, unintelligible man.