Let's begin by defining the phrase “heroic couplet.” A heroic couplet consists of two lines of rhyming verse, often in iambic pentameter (five alternating pairs of unstressed and stressed syllables). For example, in the second “epistle” of An Essay on Man, Pope declares, “Know, then, thyself, presume not God to scan; / The proper study of mankind is man.” This is a heroic couplet.
But we might wonder why we call these couplets “heroic.” Indeed, such a form is often used in poetry that narrates the tales of great heroes and their fantastic deeds. Pope's An Essay on Man does not do this. It is not even mock heroic like his satirical poem The Rape of the Lock. Yet we must recall the great task Pope has set for himself in An Essay on Man. He has determined to write what is essentially a philosophy in verse in which he discusses the relationship between humanity and the universe, the nature of human beings as individuals, the connections between human beings and society, and the possibility of human happiness. Along the way, he speaks of the dignity of human reason, the communion between God and human beings, the moral life, and the connections between human beings and nature. Indeed, the scope of this work is huge, vastly wide and deep in its subject matter. It is worthy of heroic couplets.
An Essay on Man is also eminently orderly. Pope presents his subject matter logically and clearly, and his choice of the heroic couplet ties in nicely with this characteristic. These couplets attract readers by their clarity and are easy to remember with their neatly rhymed pairs. Many of them can be easily memorized, so Pope's ideas easily stick in readers' brains, which is, of course, his whole point. He wants his readers to get to know themselves as human beings. This is a gargantuan task. We might even call it an epic task or even an heroic task. Indeed, Pope's choice of the heroic couplet is appropriate.