Le Corbusier remains a very challenging and elusive subject in architectural scholarship today due to the complexity and depth of his work. Critical analyses on his work generally stress one particular design theme or interpretive concept, such as the classical tradition, universalization, machine aesthetics, synthesis of the arts, or mysticism and ambiguity; thus, they never fully explain the depth of his art. This research demonstrates that what underlies all these concepts is Le Corbusier’s open quest for “the truth” – something that grounds the making of architectural art as well as the world in general. The search for “truth” was Le Corbusier’s major, inner concern in his formative and Purist years, and remained a central concept for him throughout his whole life – a basic and primordial abstract notion from which he derived all other concepts that defined his art works visually and structurally. To undertake such a search, with the goal of discovering fundamental “truth(s)” about the nature of things around us, is very much the paradigm of Modernity itself. The goals of this research are, first, to analyze and define more thoroughly Le Corbusier’s different interpretations of truthful architecture, and second, to explain how they were translated into visual language. Through an examination of Le Corbusier’s written works from the Purist Period (1918 to 1928), four different concepts of truth in architecture are revealed: truth of nature, lyrical truth, historical truth, and ethical truth. The research also traces the translation of these abstract ideas into the universal visual language or formal principles of his buildings, paintings, and city plans from the Purist Period. With these findings, the research offers deeper understanding of Le Corbusier’s works. The reasons why he used motifs like cubic shapes, cylindrical columns, horizontal strip windows, white plaster walls, enclosed balconies, and the other recognizable elements that distinguish his architecture, are elucidated. This research also provides new insight into his influence by the broad system of values of Modernity.