[Crossposted at OrangePhilosophy] My fellow OrangePhilosopher Dave Bzdak and I just had a conversation with Don Arentz, one of our colleagues in teaching at Le Moyne College, about what seems to be an empirical question but seems difficult to see how it might be empirical. How big is your vocabulary? It would seem that the question is indeed an empirical matter. Yet how would you go about empirically investigating it? Dave suggested maybe it would be in principle possible but only if you kept track of every single word you ever encountered to get a list of all the words that might be in your vocabulary, and then you investigated to see if they were still in your vocabulary at a given time. Could you do this, though? I'm not worrying about the possibility of coming up with a list of all the words you've ever encountered. Suppose you could do it. That's in principle possible, I would say, even if in practice it would be amazingly difficult to implement. Given that list, could you determine which of those words are in your vocabulary at any given time? It seems that, if you could, then you would know how big your vocabulary at the time was.
So suppose I want to know how many of those words are in my vocabulary right now. I could presumably go down the list to investigate which ones I know, right? I'm not sure it's so easy, though. I could recognize some words that I know. But wouldn't there be others that I know and don't recall the meaning of just by seeing the word in isolated form? There are some whose meaning I would remember if I saw it in the right sort of sentence that would trigger my memory. Of course, there would be others that I don't know but would get from context, in which case I've just added a word to my vocabulary. I shouldn't count those. I wanted to know how many were in it before I started the investigation. What if I'm not in a position to distinguish between the cases when the sentence triggers my memory of what a word means and cases when the context helps me add a new word to my vocabulary? It's not clear to me that I could tell the difference. If that's right, then the exact count of my vocabulary isn't really empirically discoverable after all. That's really weird. Does that mean the size of my vocabulary is not really an empirical question?