A Defense Against an Eliminativist Argument

Here's a quick (eliminativist) argument that there are no chairs (I've seen similar arguments):

1. Atoms arranged chair-wise can do all the same causal work that chairs would do if there were chairs over and above atoms arranged chair-wise (swivel, keep your butt from hitting the floor, etc.)
2. Ockham's Razor.
3. Thus no chairs, buildings, arms, scissors....

Most people believe that chairs exist. It's just a Moorean fact for the vast majority of people. They think they *know* that there are chairs. "Of course there are chairs!" So what should most people think about the above argument, particularly premise 1?

I think they should reject it if they also hold the following causal-epistemic principle:
C: If S knows about some x, x plays a causal role in the knowledge of x.

C is plausible--especially if we allow for more than efficient causation. If I walked into a room and saw a hologram of a telephone, forming the belief that there is a phone in the room, I don't have knowledge that there is a phone in the room even if there is one (e.g. on the other side of the room where I haven't observed). I have made no epistemic or psychological contact with the phone.

So if you think that you know there is a chair and accept C, you should think there *is* something for the chair to do in addition to the atoms arranged chair-wise, namely, play a causal role in your knowing that there are chairs. Of course this isn't an argument for the existence of chairs against the eliminativist but it neutralizes the above argument.

Trenton Merricks' reply to a similar defense against the eliminitivist is to say that once one realizes that atoms arranged chair-wise can do all that a chair could do, one's justification for believing in chairs is undermined.  To that I say that one has no justification for the existence of chairs in the first place, at least not in terms of any argument. It just seems that there are chairs. Moreover it just seems that one knows that there are chairs. How is one's justification or warrant undermined? Why is one still not entitled to this belief?