Antonyms, or words that have opposite meanings, for the phrase "art the same class as" include "different from," "unlike," and "not the same." These words convey a sense of differentiation, highlighting the unique qualities and characteristics that set something apart from others. Other antonyms might include "inferior to," "disparate," or "dissimilar." When writing, it's important to consider the various shades of meaning that different words carry and to choose the precise language that will accurately convey your message. By using antonyms and other contrasting words, you can help to emphasize the differences between things and make your writing more dynamic and engaging.