So the original argument does run:
1) humans exist entirely in space-time
2) if abstracta exist, they exist entirely outside of space-time
4) it's likely that humans cannot have knowledge to abstracta
5) if platonism is true then ~(4)
6) platonism is not true
But for (1) and (2) you substitute 'space-time' for 'the present'. Thus:
1') humans exist entirely in the present
2') future events exist entirely outside the present
But it seems to be that (1') and (2') are counterparts not of (1) and (2) but:
A) humans exists entirely here
B) if abstracta exist, they exist entirely outside of here
Which seems to be a queer formulation. I think that being in the present 'time-wise' is the equivalent to being here 'space-wise'. If you are in the present, you are located in a segment of time. If you are here, you are located in a segment of space.
Is this ok? It seems that instead of (1') and (2') we should write (A') and (B'):
A') humans exist entirely in time
B') future events exist entirely outside time
where B') is false. I think that even if (1') is the correct rendering, it is false. Consider Wes qua spacetime worm. I exist in the present, where the present is Sept. 19, 2008 @ 11:10am. If we roll back the present to Sept. 19, 2007 @11:10am I exist there as well. Now, I don't exist if we roll back the present to Sept. 19, 1983 @11:10am, since I wasn't born yet. If we roll the present to Sept. 19, 2999 @11:10am I won't exist here either, But from the time I was born until I die, any segment of time we want to make the present, I exist.
Am I correct to see a disanalogy here? Or, if there is no disanalogy, that (1') is false?