Paul is warning us against Calvanism in this verse (just kidding) Consider and stop.
Do you believe anyone who is not Calvanist is not a Christian? Consider then stop, then go a little, stop again, and consider.
Contrary to what baseline? What made Calvanism the baseline? Stop, then move forward a tiny bit, then consider, then eat a sandwhich, then consider some more, then stop again, repeat if necessary.
The future, since it hasn't happened yet, is not knowable. For instance, God doesn't know the color of the Easter Bunny's eyes, since the Easter Bunny doesn't exist. Does that limit God? Carefully consider, then even more carefully stop, move to the right, then consider some more, throw salt over your shoulder, and stop again.
What is serious is your idea that if people aren't Calvanist, then they aren't Christian. Only consider this one, no stopping needed.
Revelation 8:1
1 When He opened the seventh seal, there was silence in heaven for about half an hour. NKJV
Hmmm . . . a half an hour in heaven? God is constrained by time?
Hebrews 10:13
13 from that time waiting till His enemies are made His footstool. NKJV
God is waiting for something?
Tell me where in the Bible did God create time? Time isn't a thing.
This time consider, then stop, then tilt your head to the left, consider some more, move a little forward, stop agian, consider, then run foward really fast, come to a sudden stop, and consider.