Beauty and folly are old companions.
Franklin links physical beauty with folly in a deliberately compressed proverb. The saying reflects a long-standing suspicion that attractiveness can encourage vanity, indulgence or poor judgement, particularly when a person receives admiration without having to develop other qualities. Beauty, in this sense, is presented as something that may be accompanied by foolishness rather than as evidence of merit.
The remark is a generalisation rather than a literal claim that attractive people lack intelligence or good judgement. Its broader point is about the danger of judging people primarily by appearance or allowing beauty to substitute for character. Franklin’s phrase can therefore be read as a warning against overvaluing outward attractiveness, both in oneself and in others. The contrast encourages attention to qualities such as judgement, restraint and conduct, which cannot be inferred from appearance alone.