Change happens more efficiently when we have both.
Often, they’re not individuals. It could be a status quo or a system.
In the early days of the Mac, Jobs chose Microsoft to be Apple’s adversary. But keeping the focus on them too long was an expensive and distracting mistake.
An adversary focuses the mission, but it also gives agency and leverage to the opponent.
It helps to have accomplices, leverage and a focus for the long haul as well.