 Though Plato and Aristotle disagree on what beauty is, they both regard it as objective in the sense that it is not localized in the response of the beholder. The classical conception  (see below)  treats beauty as a matter of instantiating definite proportions or relations among parts, sometimes expressed in mathematical ratios, for example the ‘golden section.’ The sculpture known as ‘The Canon,’ by Polykleitos (fifth/fourth century BCE), was held up as a model of harmonious proportion to be emulated by students and masters alike: beauty could be reliably achieved by reproducing its objective proportions. Nevertheless, it is conventional in ancient treatments of the topic also to pay tribute to the pleasures of beauty, often described in quite ecstatic terms, as in Plotinus: “This is the spirit that Beauty must ever induce: wonderment and a delicious trouble, longing and love and a trembling that is all delight” (Plotinus 23, [Ennead I, 3]).