Vitruvius iterum et Frontinus à Iocundo revisi repurgatique quantum ex collatione licuit

...seemed to pursue a shadow, not the thing itself. But those who have mastered both, being as it were armed with all weapons, have more quickly and with authority attained what was proposed. For in all things, but especially in architecture, these two are present: that which is signified, and that which signifies. The signified is the proposed matter of which we speak. This, the demonstration explained by the principles of learning, signifies. Therefore, it seems that he who professes to be an architect must be trained in both parts. Thus, it is necessary for him to be both naturally gifted and teachable for learning. For neither natural talent without discipline, nor discipline without natural talent, can make a perfect artist; and he must be literate, skilled in drawing, learned in geometry, not ignorant of optics, instructed in arithmetic, have knowledge of many histories, have listened diligently to philosophers, have known music, not be ignorant of medicine, know the opinions of legal experts, and have knowledge of astrology and the principles of the heavens. The reasons why these things are so are as follows. It is fitting for an architect to know literature so that he can make his memory firmer through commentaries. Then, to have the knowledge of drawing, so that he may more easily be able to represent by painted models the appearance of the work he desires. Geometry, however, provides many aids to architecture; first, it teaches the use of the compass from straight lines, from which the descriptions of buildings on sites are more easily expedited, as well as the directions of squares, levels, and lines. Likewise, through optics, the light of the heavens is correctly directed in buildings from the regions of the art. Through arithmetic, the costs of buildings are calculated, the principles of measurements are explained, and difficult questions of symmetry are found by geometric principles and methods.