The Figures which excite in us the Ideas of Beauty, seem to be those in which there is Uniformity amidst Variety. There are many Conceptions of Objects which are agreeable upon other accounts, such as Grandeur, Novelty, Sanctity, and some others, which shall be mention'd hereafter. But what we call Beautiful in Objects, to speak in the Mathematical Style, seems to be in a compound Ratio of Uniformity and Variety: so that where the Uniformity of Bodies is equal, the Beauty is as the Variety; and where the Variety is equal, the Beauty is as the Uniformity. This may seem probable, and hold pretty generally.
Francis Hutcheson, An Inquiry into the Original of Our Ideas of Beauty and Virtue, 1.2.3.