The purpose of this article is to apply the Threefold Laws of Meaning, developed by Lady Welby, to the Corinthian order of the Basilica of San Lorenzo in Florence so as to analyze the morphological differences and symbols of its architectural order from 1420, when the construction of the new plan for the Basilica commissioned by Giovanni di Averardo dei Medici and designed by Brunelleschi started, to 1490, when it came to its completion under Lorenzo de Medici and the supervision of Giuliano da Sangallo. It will demonstrate how Lady Welby’s threefold laws of meaning can be successfully used to comprehend, through signs, the historical evolution of the Basilica and the transformation of architectural thought in the 15th century
