Magic: The Gathering Comprehensive Rules Changes - Planar Chaos to Future Sight

Old rule (Planar Chaos)	New rule (Future Sight)
424.2. [Click to view all changes.]
	424.2. A player can't pay a cost unless he or she has the necessary resources to pay it fully. For example, a player with only 1 life can't pay a cost of 2 life, and a permanent that's already tapped can't be tapped to pay a cost. See rule 203, "Mana Cost and Color," and rule 403, "Activated Abilities."

Old rule (Planar Chaos)

New rule (Future Sight)

424.2.

A player can't pay a cost unless he or she has the necessary resources to pay it fully. For example, a player with only 1 life can't pay a cost of 2 life, and a permanent that's already tapped can't be tapped to pay a cost. See rule 203, "Mana Cost and Color," and rule 403, "Activated Abilities."