What literary device is primarily used to compare two unlike things without using "like" or "as"?

The correct answer is metaphor. This literary device involves a direct comparison between two unlike things without the use of "like" or "as," which distinguishes it from a simile. By asserting that one thing is another, metaphors create strong imagery and evoke deeper connections and meanings through that association. For example, saying "Time is a thief" conveys the idea that time stealthily takes away moments from our lives, enabling the reader to grasp the concept in a more profound way.

Simile, on the other hand, would explicitly use "like" or "as" to draw comparisons. Allusion refers to indirect references to other works, events, or figures, relying on the reader's familiarity with the subject. Oxymoron involves the juxtaposition of contradictory terms, creating a paradoxical effect. Each of these options serves distinct roles in literature, but metaphor is specifically designed for implicit comparisons, making it the most fitting answer in this context.