Final answer:
Antithetical parallelism is the type of parallelism where antonyms are used to express the same thought with contrast. Assonance refers to the repetition of vowel sounds and contributes to the rhythm and aural quality of literature, different from the contrasting nature of antithetical parallelism. Repetition and parallelism often work together to enhance rhetorical effectiveness.
Step-by-step explanation:
The type of parallelism that is used when the same thought is expressed using antonyms is called antithetical parallelism. In the context of English grammar and rhetoric, parallelism is a figure of speech where similar grammatical forms or structures are used to express related ideas, thereby creating a pattern that can make the expression more memorable, persuasive, and impactful. When antonyms are used to achieve this parallel structure, it serves to highlight the contrasts between the ideas being expressed, providing a clear juxtaposition that can enhance the overall messaging and add a layer of complexity in the composition.
Assonance, on the other hand, is a literary device where vowel sounds are repeated within close proximity inside a passage, contributing to the rhythm and aural quality of the text. This is quite different from the use of parallelism through antonyms. An example of assonance is visible in the work of Edgar Allen Poe: "Once upon a midnight dreary, while I pondered weak and weary...". Although assonance can enhance the harmony and flow of a sentence or stanza, it doesn't necessarily involve parallelism or the contrast created by antonyms.
It is worth noting, however, that repetition and parallelism can coincide as rhetorical strategies to reinforce certain themes or ideas, as demonstrated in President John F. Kennedy's inaugural address, where he skillfully uses these devices to anchor his intentions for the nation's collaborative effort towards liberty.