The spelling of the phrase "art the opinion" may seem unusual to some, but it is simply an archaic way of saying "are the opinion." The word "art" is pronounced /ɑːt/ in IPA phonetic transcription, which is the same as the modern word "are." This kind of spelling is sometimes found in older texts, but is not commonly used in modern English. It's important to be aware of these variations in spelling to understand and appreciate the history of the language.