Freewill theists typically act as though the distinction between God "causing" evil and God "permitting" evil is morally crucial. I'm going to develop an illustration by philosopher Stephen Mumford which a friend shared with me. Ironically, I like his illustration, but disagree with his interpretation.
Take a tug-of-war. Suppose you begin with two evenly-matched teams. They may be evenly matched because both sides have an equal number of teammates, and each teammate is equal in size and strength to his fellow teammates, as well as the opposing teammates. They are numerically and individually equally matched.
Or they may be aggregately evenly matched. Maybe one side has fewer teammates than the other, but its teammates are bigger and stronger than the opposing side, as a result of which each team pulls with the same amount of force. The qualitative advantages balance out the quantitative disadvantages, or vice versa.
This results in a stalemate. Neither team can win.
So what would it take for one team to win? There are two ways that could happen.
i) By adding another teammate to one side. That would tip the balance of power in its favor.
ii) By subtracting a teammate from one side. That, too, would shift the balance of power.
We might say adding a teammate causes that team to win the tug of war. Just enough extra force.
But by converse logic, we might say subtracting a teammate causes that team to lose. Indeed, it's hard to see how that inference can be avoided. As philosopher David Lewis once said: "We think of a cause as something that makes a difference."
If a teammate decided to quit, he'd naturally be blamed for causing his team to lose. His team lost when he stopped pulling the rope. It was a group effort which could not afford a single defection.
The opposing team won because his team lost, and his team lost because he gave up. In that respect, he caused the opposing team to win. It couldn't win unless his team lost. His team losing was a necessary and sufficient condition of their winning. He made it happen. His action was the differential factor. The tipping point.
Furthermore, we could recast the issue in terms of rendering an outcome certain. In this case, not pulling ensured defeat. Just as adding a teammate guaranteed (or determined) victory for one side, subtracting a teammate guaranteed (or determined) defeat for the other side.