Lupin not being a detective
It does sound logical to say that Lupin is only a thief but I guess we would also need to edit Wikipedia's page about Maurice Leblanc then, as the information was taken from there and it still says that right now (i.e. that Lupin is both a thief and detective -- and yeah, I know that Wikipedia is not always the most accurate source, just mentioning we'd need to correct it there eventually too). Note that even though he may not be a detective by profession, he may nonetheless have the traits of one or do things in similar ways which would explain why he is informally described as one. For example, even though Shinichi is only a high-school student, he calls himself a detective as he thinks, reasons and does things like one. Hence why Lupin, in this case, may have been described as both..
Another reason to think this way is by how the character is portrayed in Maurice Leblanc's work. One good example would be the short stories featuring "Arsène Lupin against Sherlock Holmes". To sum up, Lupin isn't just a simple thief. He's a bit like Kaitou Kid as they both think like a detective. --Maurice 16:50, 24 April 2010 (UTC)