Recently some academics, notably Simon James and John Collis, have challenged the use of the term 'Celtic'. They draw attention to the limited reference by classical writers to the Celts.

During the first Celtic revival in the seventeenth century, the word was used to define the Celtic family of languages. Linguists identify two families of Celtic languages: Q-Celtic or Goidelic (Irish, Scots Gaelic and Manx) and P-Celtic or Brythonic (Welsh, Breton and Cornish). In the past, it was believed that each language family represented a wave of Celtic migrants moving from central Europe into Britain and Ireland. This theory has now been superseded. One idea is that the Celtic languages evolved gradually across a large area, rather than rapidly originating from a single source. The Celtic language family is only one of the Indo-European language group, which has evolved since early prehistory.

The idea of a pan-European 'Celtic Society' and belief system prior to Roman conquest, is now seen as over simplistic and inaccurate. Instead the archaeological evidence shows strong regional contrasts, which suggests a mosaic of diverse societies across Europe. Each had its own beliefs and customs. Reading the past in this way celebrates the interpretation of societies as being diverse and dynamic.