The Celts did not have a caste society, though there were well-defined classes. At the top was the noble class. At some periods of Celtic history, the top man was a king. Often, the king was the head man of an indivudual tribe, though in later times, nations composed of several tribes came under royal rule. In its most refined form, kingship was seen as divine - rulers were men through whom the gods spoke. Kingship was not necessarily inherited, for kings could nominate their successor. The law of royal succession among the Picts was through the mother, though invariably the monarch was male, and often the king's father was a foreighner. There were also queens, who sometimes ruled in their own right. Among them are the legendary Irish warrior queen, Maeve, and the British Boudicca, who led the rebellious Iceni against Roman rule in AD 61.
But kingship was not the only form of rule. In Gaul, before the Roman conquest, kingship was abolished by several tribes, including the Aedui, Lexovii, Lemovices, Santones, Remi, and Treviri. Instead of a king, a magistrate, the Vergobret, elected by the nobility, headed the tribe. The real power was in the hands of the noble class, whose status came from hereditary right. Noble lineages contained men of honorable origin, linked to other families through marriage alliances. They owned the land, and from their ranks came the military generals and the Druids. In Wales, this class, the cenedl, ruled util the Norman conquest.
However in Celtic society there was not a rigid class system imposed by birth. The landless commoners had the possiblility of personal advancement by making a fortune through commerce or war. Some of the lower orders who had fallen upon hard times became clients, having pledged themselves to serve a powerful nobleman. But such an obligation was different from slavery, and the commoner did not give up his rights. Caesar wrote that the object of clientage was to ensure that all common people should have protection against powerful people. Each nobleman had to guarantee that no harm should come to him supporters. If it did, he lost face, and fell in status. Clientage was a form of social welfare, with obligations on both sides. The nobleman supported the client with gifts, that required repayment by loyal service. Unlike some societies, where slavery was hereditary, and there was no chance of future generations becoming free,the Celts' slaves were captive foreigners without civil rights. They could always be freed, to become the client of the noble who had freed them.
Slaves could not fight in times of war. Other men had the right to bear arms, but not all, for some were only permitted to fight when their lives were threatened. In Gaul, it was only possible to go to war if the common people and the priesthood consented, having received favorable omens. Although there was always a commander-in-chief, wars were conducted by an assembly called the Armed Council, that had the final say on strategic matters. Several times during the Gallic War that Caesar won, the Gaulish commander, Vercengetorix, had to give account of his conduct of the war to the Armed Council.
The Roman author Strabo wrote that among the Gauls there wer three groups of men who were held in exceptional honor: the Bards, the Vates, and the Druids. The Bards were the musicians, singers, and poets. The Vates were soothsayers, diviners, and natural diviners. Ancient Celtic religion, that underpinned every aspect of everyday life, was nature-venerating and polytheistic, recognizing many levels of supernatural beings and divinities, female as well as male. The Celts believed that the course of nature is the will of the Gods. Thus they venerated both local and general deities, usually in natural sanctuaries, especially shrines at ssprings, rivers, lakes, and in woodland. The Bards, Vates, and Druids had an integrated relationship with the natural world. They possessed an immense body of traditional lore, concerning nature, the seasons, astronomy, death, and transformation. Most of the ancient skills and wisdom of these men are known still, underlying contemporary Celtic spirituality, that is the synthesis of Celtic Spirituality, that is essential for a continuing, living tradition.