Phallic amulets like this were often hung in the doorways of Roman houses and shops, together with a lamp, to protect against evil spirits, and the sound of the bells attached to them was also believed to serve the same purpose. These aggressively male objects were not considered to be erotic, but as signs and bringers of prosperity, owing to their reproductive ability. For the same reason phallic motifs were often found on terracotta plaques set into the outer walls of buildings, particularly at street corners, for example at Pompeii. The symbol is linked with the god Priapus, who was always depicted with a grossly exaggerated and erect penis. Images of him were popular in wall-painting and as bronze statuettes. As well as being considered a protector of property he was the god of the fertility of gardens and farms. In the second half of the eighteenth century a number of collectors and antiquarians showed a serious interest in 'erotica'. Charles Townley, the important collector who owned this piece, and his friends Sir William Hamilton and Richard Payne Knight argued that the ultimate origins of all human religious thought lay in priapism, the worship of the phallus as the symbol of the creative principle.