The earliest surviving written work on the subject of architecture is De architectura, by the Roman architect Vitruvius in the early 1st century AD. According to Vitruvius, a good building should satisfy the three principles of firmitas, utilitas, venustas, commonly known by the original translation – firmness, commodity and delight. An equivalent in modern English would be: Durability – a building should stand up robustly and remain in good condition. Utility – it should be suitable for the purposes for which it is used. Beauty – it should be aesthetically pleasing. According to Vitruvius, the architect should strive to fulfill each of these three attributes as well as possible. Leone Battista Alberti, who elaborates on the ideas of Vitruvius in his treatise, De Re Aedificatoria, saw beauty primarily as a matter of proportion, although ornament also played a part. For Alberti, the rules of proportion were those that governed the idealised human figure, the Golden mean. The most important aspect of beauty was therefore an inherent part of an object, rather than something applied superficially; and was based on universal, recognisable truths. The notion of style in the arts was not developed until the 16th century, with the writing of Vasari: by the 18th century, his Lives of the Most Excellent Painters, Sculptors, and Architects had been translated into Italian, French, Spanish and English.