JANUS, in Roman mythology one of the principal Italian deities. The name is generally explained as the masculine form of Diana (Jana), and Janus as originally a god of light and day, who gradually became the god of the beginning and origin of all things. According to some, however, he is simply the god of doorways (januae) and in this connexion is the patron of all entrances and beginnings. According to Mommsen, he was " the spirit of opening," and the double-head was connected with the gate that opened both ways. Others, attributing to him an Etruscan origin, regard him as the god of the vault of heaven, which the Etruscan arch is supposed to resemble. The rationalists explained him as an old king of Latium, who built a citadel for himself on the Janiculum. It was believed that his worship, which was said to have existed as a local cult before the foundation of Rome, was introduced there by Romulus, and that a temple was dedicated to him by Numa. This temple, in reality only an arch or gateway (Janus geminus) facing east and west, stood at the north-east end of the forum. It was open during war and closed during peace (Livy i. 19); it was shut only four times before the Christian era. A possible explanation is, that it was considered a bad omen to shut the city gates while the citizens were outside fighting for the state; it was necessary that they should have free access to the city, whether they returned victorious or defeated. Similarly, the door of a private house was kept open while the members of the family were away, but when all were at home it was closed to keep out intruders. There was also a temple of Janus near the theatre of Marcellus, in the forum olitorium, erected by Gaius Duilius (Tacitus, Ann. ii. 49), if not earlier.
The beginning of the day (hence his epithet Matutinus), of the month and of the year (January) was sacred to Janus; on the gth of January the festival called Agonia was celebrated in his honour. He was invoked before any other god at the beginning of any important undertaking; his priest was the Rex Sacrorum, the representative of the ancient king in his capacity as religious head of the state. All gateways, housedoors and entrances generally, were under his protection; he was the inventor of agriculture (hence Consivius, " he who sows or plants "), of civil laws, of the coining of money and of religious worship. He was worshipped on the Janiculum as the protector of trade and shipping; his head is found on the as, together with the prow of a ship. He is usually represented on the earliest coins with two bearded faces, looking in opposite directions; in the time of Hadrian the number of faces is increased to four. In his capacity as porter or doorkeeper he holds a staff in his right hand, and a key (or keys) in his left; as such he is called Patulcius (opener) and Clusius (closer). His titles Curiatius, Patricius, Quirinus originate in his worship in the gentes, the curiae and the state, and have no reference to any special functions or characteristics. In late times, he is both bearded and unbearded; in place of the staff and keys, the fingers of his right hand show the number 300 (CCC.), those of his left the number of the remaining days of the year (LXV.). According to A. B. Cook (Classical Review, xviii. 367), Janus is only another form of Jupiter, the name under which he was worshipped by the pre-Latin (aboriginal) inhabitants of Rome; after their conquest by the Italians, Janus and Jana took their place as independent divinities by the side of the Italian Jupiter and Juno. He considers it probable that the three-headed Janus was a triple oak-god worshipped in the form of two vertical beams and a cross-bar (such as the ligillum sororium, for which see HORATII); hence also the door, consisting of two lintels and side-posts, was sacred to Janus. The three-headed type may have been the original, from which the two-headed and four-headed types were developed. J. G. Frazer (The Early History of the Kingship, pp. 214, 285), who also identifies Janus with Jupiter, is of opinion that Janus was not originally a doorkeeper, but that the door was called after him, not vice versa. Janua may be an adjective, janua foris meaning a door with a symbol of Janus close by the chief entrance, to serve as a protection for the house; then janua alone came to mean a door generally, with or without the symbol of Janus. The double head may have been due to the desire to make the god look both ways for greater protection. By J. Rhys (Hibberl Lectures, 1886, pp. 82, 94) Janus is identified with the three-faced ( sometimes three-headed) Celtic god Cernunnus, a chthonian divinity, compared by Rhys with the Teutonic Heimdal, the warder of the gods of the under- world; like Janus, Cernunnus and Heimdal were considered to be the Jons et origo of all things.
See S. Linde, De Jano summo romanorum deo (Lund, 1891); J. S. Speyer, " Le Dieu remain Janus," in Revue de I'histoire des religions (xxvi., 1892); G. Wissowa, Religion und Kultus der Romer (1902); W. Deecke, Etruskische Forschungen, vol. ii.; W. Warde Fowler, The Roman Festivals of the Period of the Republic (1899), pp. 282-290; articles in W. H. Roscher's Lexikon der Mythologie and Daremberg and Saglio's Dictionnaire des Antiquites; J. Toutain, Etudes de Mythologie (1909). On other jani (arched passages) in Rome, frequented by business men and money changers, see O. Richter, Topographic der Stadt Rom (1901). (J. H. F.)
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)