The late Middle Ages saw widespread changes to English pronunciation. By the mid-16th century, the language had dropped the final syllables on many words, giving English one of the highest concentrations of monosyllables. Since the Renaissance effort to use classical poetic forms with English words, critics have generally frowned on long strings of monosyllables as lacking poetic rhythm. Many 20th-century critics have echoed this disdain, while others argue that monosyllables can have a powerful effect in poetry.
Unlike words with multiple syllables, an entire monosyllabic word must be either stressed or unstressed. In a poetic line, that stress depends on the part of speech -- nouns and verbs are more frequently stressed than participles are, for example -- but also on the word’s meaning in context. Monosyllabic lines thus give poets the power to have an entire line feel stressed or unstressed. One effect of an entirely unstressed line can be monotony, conveying feelings like boredom or drudgery. Alexander Pope’s “Essay on Criticism” illustrates this phenomenon while discussing it, frowning on poems in which “ten low Words oft creep in one dull Line.”
While monosyllables can convey monotony when they are all unstressed, a line packed with emphatic monosyllables can have greater impact than one in a standard stress scheme like iambic pentameter or trochaic tetrameter. In “Paradise Lost,” for instance, Satan uses monosyllables to drive home the power of perspective: “The mind is its own place, and in it self/Can make a Heav’n of Hell, a Hell of Heav’n.” The words “mind,” “is,” “own,” “place,” “make,” “Heav’n” and “hell,” all stressed here, would lose emphasis if portions of them were unstressed. Perhaps this explains Milton’s decision to contract the two-syllable word “Heaven” to the monosyllable “Heav’n.”
Finally, monosyllables’ flexibility in terms of stress allows readers to interpret some lines in a variety of ways. For instance, actors can speak the famous opening line to Hamlet’s soliloquy in William Shakespeare’s “Hamlet” with several different emphases: “To be or not to be, that is the question.” Actors must decide whether Hamlet stresses “that” over “is,” or vice versa; whether he equally stresses “to,” “be” and “not,” and whether to emphasize “the.”