Other writers argue that we do not find Druids existing in the Danube region, in Cisalpine territory, nor in Transalpine Gaul, "outside the limits of the region occupied by the Celtæ."959 This could only have weight if any of the classical writers had composed a formal treatise on the Druids, showing exactly the regions where they existed. They merely describe Druidism as a general Celtic institution, or as they knew it in Gaul or Britain, and few of them have any personal knowledge of it. There is no reason to believe that Druids did not exist wherever there were Celts. The Druids and Semnotheoi of the Celts and Galatæ referred to c. 200 B.C. were apparently priests of other Celts than those of Gaul, and Celtic groups of Cisalpine Gaul had priests, though these are not formally styled Druids.960 The argument ex silentio is here of little value, since the references to the Druids are so brief, and it tells equally against their non-Celtic origin, since we do not hear of Druids in Aquitania, a non-Celtic region.961
The theory of the non-Celtic origin of the Druids assumes that the Celts had no priests, or that these were effaced by the Druids. The Celts had priests called gutuatri attached to certain temples, their name perhaps meaning "the speakers," those who spoke to the gods.962 The functions of the Druids were much more general, according to this theory, hence M. D'Arbois supposes that, before their intrusion, the Celts had no other priests than the gutuatri.963 But the probability is that they were a Druidic class, ministers of local sanctuaries, and related to the Druids as the Levites were to the priests of Israel, since the Druids were a composite priesthood with a variety of functions. If the priests and servants of Belenos, described by Ausonius and called by him oedituus Beleni, were gutuatri, then the latter must have been connected with the Druids, since he says they were of Druidic stock.964 Lucan's "priest of the grove" may have been a gutuatros, and the priests (sacerdotes) and other ministers (antistites) of the Boii may have been Druids properly so called and gutuatri.965 Another class of temple servants may have existed. Names beginning with the name of a god and ending in gnatos, "accustomed to," "beloved of," occur in inscriptions, and may denote persons consecrated from their youth to the service of a grove or temple. On the other hand, the names may mean no more than that those bearing them were devoted to the cult of one particular god.
Our supposition that the gutuatri were a class of Druids is supported by classical evidence, which tends to show that the Druids were a great inclusive priesthood with different classes possessing different functions—priestly, prophetic, magical, medical, legal, and poetical. Cæsar attributes these to the Druids as a whole, but in other writers they are in part at least in the hands of different classes. Diodorus refers to the Celtic philosophers and theologians (Druids), diviners, and bards, as do also Strabo and Timagenes, Strabo giving the Greek form of the native name for the diviners, (ouateis), the Celtic form being probably vátis (Irish, fáith).966 These may have been also poets, since vátis means both singer and poet; but in all three writers the bards are a fairly distinct class, who sing the deeds of famous men (so Timagenes). Druid and diviner were also closely connected, since the Druids studied nature and moral philosophy, and the diviners were also students of nature, according to Strabo and Timagenes. No sacrifice was complete without a Druid, say Diodorus and Strabo, but both speak of the diviners as concerned with sacrifice. Druids also prophesied as well as diviners, according to Cicero and Tacitus.967 Finally, Lucan mentions only Druids and bards.968 Diviners were thus probably a Druidic sub-class, standing midway between the Druids proper and the bards, and partaking of some of the functions of both. Pliny speaks of "Druids and this race of prophets and doctors,"969 and this suggests that some were priests, some diviners, while some practised an empiric medical science.
On the whole this agrees with what is met with in Ireland, where the Druids, though appearing in the texts mainly as magicians, were also priests and teachers. Side by side with them were the Filid, "learned poets,"970 composing according to strict rules of art, and higher than the third class, the Bards. The Filid, who may also have been known as Fáthi, "prophets,"971 were also diviners according to strict rules of augury, while some of these auguries implied a sacrifice. The Druids were also diviners and prophets. When the Druids were overthrown at the coming of Christianity, the Filid remained as a learned class, probably because they had abandoned all pagan practices, while the Bards were reduced to a comparatively low status. M. D'Arbois supposes that there was rivalry between the Druids and the Filid, who made common cause with the Christian missionaries, but this is not supported by evidence. The three classes in Gaul—Druids, Vates, and Bards—thus correspond to the three classes in Ireland—Druids, Fáthi or Filid, and Bards.972
We may thus conclude that the Druids were a purely Celtic priesthood, belonging both to the Goidelic and Gaulish branches of the Celts. The idea that they were not Celtic is sometimes connected with the supposition that Druidism was something superadded to Celtic religion from without, or that Celtic polytheism was not part of the creed of the Druids, but sanctioned by them, while they had a definite theological system with only a few gods.973 These are the ideas of writers who see in the Druids an occult and esoteric priesthood. The Druids had grown up pari passu with the growth of the native religion and magic. Where they had become more civilised, as in the south of Gaul, they may have given up many magical practices, but as a class they were addicted to magic, and must have taken part in local cults as well as in those of the greater gods. That they were a philosophic priesthood advocating a pure religion among polytheists is a baseless theory. Druidism was not a formal system outside Celtic religion. It covered the whole ground of Celtic religion; in other words, it was that religion itself.
The Druids are first referred to by pseudo-Aristotle and Sotion in the second century B.C., the reference being preserved by Diogenes Laertius: "There are among the Celtæ and Galatæ those called Druids and Semnotheoi."974 The two words may be synonymous, or they may describe two classes of priests, or, again, the Druids may have been Celtic, and the Semnotheoi Galatic (? Galatian) priests. Cæsar's account comes next in time. Later writers gives the Druids a lofty place and speak vaguely of the Druidic philosophy and science. Cæsar also refers to their science, but both he and Strabo speak of their human sacrifices. Suetonius describes their religion as cruel and savage, and Mela, who speaks of their learning, regards their human sacrifices as savagery.975 Pliny says nothing of the Druids as philosophers, but hints at their priestly functions, and connects them with magico-medical rites.976