I am saying that you cannot claim to be undecided if you have already rejected one of the choices. Choice 3 is impossible to make if Choice 1 (or 2) has been eliminated.
It is possible to be undecided, just not once you have crossed out one of the options.
I disagree. In fact, that's the whole point I've been trying to argue: failing to assent to one proposition doesn't necessarily imply assenting to its opposite.
This is what I was trying to demonstrate with my "breakfast" question many pages back: If I tell you "I had eggs for breakfast", you might not automatically accept it, but the fact that you didn't accept it doesn't mean that you accept that I
didn't have eggs for breakfast. Instead, you can reserve judgement. Maybe you'll choose one of those options later, and maybe you won't.
Here's a hypothetical example: let's say for argument's sake that you know I'm a really untrustworthy guy. You don't believe anything I say without independent corroboration.
Say I come up to you and say "I had eggs for breakfast". Do you believe me? I'm untrustworthy, so probably not. You don't accept my claim.
Now... let's take the approach you suggested: take the failure to accept a claim as acceptance of its negation. So, because you don't believe me when I say "I had eggs for breakfast", you decide that it's actually true that I
didn't have eggs for breakfast.
However, let's consider the scenario again, but with one change: when I come up to you, instead of saying to you "I had eggs for breakfast", I say "I
didn't have eggs for breakfast".
The rest of the scenario plays out as before: because I'm an untrustworthy guy, you don't accept my claim and instead accept its negation; you decide that I actually
did have eggs for breakfast.
So... in the two cases, you came to the exact opposite conclusion, and the only difference between the scenarios was that you were presented with an unsupported claim from an untrustworthy person... IOW, something that should carry no weight at all in a logical determination of what's true. IMO, this is problematic.
Does that help you see what I'm getting at?