Lucretius, therefore, gains moral elevation by deserting the conclusion of Epicurus. While he does full justice to the poetical side of pleasure as an end in itself, [64] he never insists on it as a motive to action. Thus he retains the conception as a noble ornament of his verse, but reserves to himself, as every poet must, the liberty to adopt another tone if he feels it higher or more appropriate. Indeed, logical consistency of view would be out of place in a poem; and Lucretius is nowhere a truer poet that when he sins against his own canons. [65] His instinct told him how difficult it was to combine clear reasoning with a poetical garb, especially as the Latin language was not yet broken to the purposes of philosophy. [66] Nevertheless so complete is his mastery of the subject that there is scarcely a difficulty arising from want of clearness of expression from beginning to end of the poem. There are occasional _lacunae_, and several passages out of place, which were either stop-gaps intended to be replaced by lines more appropriate, or additions made after the first draft of the work, which, had the author lived, would have been wrought into the context. The first three books are quite or nearly quite finished, and from them we can judge his power of presenting an argument. His chief object he states to be not the discovery, but the exposition of truth, for the purpose of freeing men's minds from religious terrors. This he announces immediately after the invocation to Venus, "Mother of the Aeneadae," with which the poem opens. He then addresses himself to Memmius, whom he intreats not to be deterred from reading him by the reproach of "rationalism." [67] He next states his first principle, which is the denial of creation: "Nullam rem e nilo gigni divinitus unquam,"