This has been bugging me for awhile now. When a card like {Jace, Architect of Thought} says to make two piles, and i make the piles can my opponent look at the piles?
I don't think there are cards where you make piles for yourself to choose. That being said, unless the card say reveal cards, you don't need to.
Yes, they CAN look at the piles
RESOLVED
Thats the point of the card. They look at the piles and decide if they want more cards or if the smaller pile is more worth it.
It literally says "reveal".