There seems to be at least 3 main theories and depending on who you read is what you get for an answer. Most of these theories are based on archeology, toponymic evidence and written evidence. It seems depending on the authors predisposition is what leads to a particular conclusion.
The "Celtic" historian see's the Belgae as "Celtic" claiming the toponyms as being "Celtic" as are the names and most of the archaeological finds. The written evidence, especially by Caesar is usually seen as political and has no bearing on the reality of the situation.
The "Germanic" historian see's the toponyms as being early German and agreeing with the writings of the Romans of the time(Caesar, Tacitus, etc.) while the archaeological and some of the names as being "Celtisized".
The third is that being of the Nordwest block which is similar to the "Germanic" view except they say the Belgae were neither "Germanic" nor "Celts".
Without siting wikipedia, is there any books (post the year 2,000) or good links that discuss the origins of the Belgae?