Poetry interprets in two ways: it interprets by expressing, with magical felicity, the physiognomy and movements of the outward world; and it interprets by expressing, with inspired conviction, the ideas and laws of the inward world of man's moral and spiritual nature. In other words, poetry is interpretative both by having natural magic in it, and by having moral profundity.
Matthew ArnoldIndeed there can be no more useful help for discovering what poetry belongs to the class of the truly excellent, and can therefore do us most good, than to have always in one's mind lines and expressions of the great masters, and to apply them as a touchstone to other poetry.
Matthew Arnold