Even if we consider not words by themselves but rules deciding what words may appropriately be produced in certain contexts - even if we consider, in computer jargon, programs for using words - unless those programs themselves refer to something extra-linguistic there is still no determinate reference that those words possess. This will be a crucial step in the process of reaching the conclusion that the Brain-in-a-Vat Worlders cannot refer to anything external at all (and hence cannot say that they are Brain-in-a-Vat Worlders).