Which term exemplifies a phrase that juxtaposes contradictory concepts?

The term that exemplifies a phrase that juxtaposes contradictory concepts is an oxymoron. An oxymoron brings together two opposing ideas to create a new meaning or to highlight a particular quality that might not be obvious when considering the words separately. Common examples include phrases such as "deafening silence" or "bittersweet," which showcase how combining contradictory terms can enhance the expression or evoke a deeper understanding of a concept.

The other choices do not fit the definition of juxtaposing contradictory concepts. Aphorisms are succinct statements that express a general truth or principle but do not inherently contain contradictions. A syllogism is a form of logical reasoning where a conclusion is drawn from two premises, none of which involve contradictory terms. Argumentum ad Hominem refers to a fallacy where an argument is countered by attacking the character of the person making it, rather than addressing the argument itself, which also does not entail the juxtaposition of contradictory concepts.