GENIUS, in Antiquity, the tutelary spirit that watched over the destinies of nations, and of each individual. The idea of the genius, or δαίμων, is first met with in the mythology of the Greeks. Homer makes no mention of these dæmones; but Hesiod accounts for their origin by describing them as the souls of good men who lived in the golden age. According to him, they are 30,000 in number: their functions are to watch over the human race and carry out the will of Jove, unseen by mortal eye. This conception was taken up by the Platonists, who assigned to every man at his birth a good and an evil dæmon. According as either of these was in the ascendant, the life of the individual was influenced for good or evil. The beautiful conversations of Socrates on his good and evil genius are familiar to all who have read the works of Plato.
Like the dæmones of the Greeks, the genii of the Romans were tutelary or guardian spirits; but their functions began at a still earlier period. They were in fact (as the etymology of their name implies) the producing or life-giving powers which organized the being whom it was their duty to protect till death. On this account also the nuptial bed was called the lectus genialis. By every Roman citizen the genius was worshipped with especial honour, and a birthday was celebrated with offerings of the finest flowers and wine to them. Every one thought it at once a duty and a privilege to "indulge his genius" (indulgere genio), i.e. to enjoy to the utmost the merriment allowed on these occasions.
In the Roman mythology genii were not confined to the human race alone. Every living being, and even every place, had a guardian spirit of its own. These local genii were symbolized under the form of a serpent (the type of renovation) eating fruit placed before him. (Plutarch, De Genio Socratis; Hartung, Die Reliq. der Rom.; Smith's Diet. of Gr. and Rom. Antiq., &c.)