Can God make a square circle? Can God make a stone so heavy that He can't lift it? Can God check mate you in chess with just His king? Can God learn something new? Can God get better at something? Can God improve Himself?
All of these questions have the fundamental problem of being illogical.The questions are invalid because the questions contradicts itself by not describing an actual action. When a person says "make a square circle" or "check mate me in a game of chess with just your king" they have contradicted themselves in an action to be preformed. Logically, any question which contradicts itself isn't a valid question.
Therefore, when someone asks "Can God reach the ends of greater good without the means of suffering", they have contradicted themselves in an action to be preformed in the same way that the person who asks about God making a stone so heavy that He can't lift it contradicts themselves in describing an action to be preformed.
So, to respond to the question "How can you call God all-powerful if He cannot reach the ends without the means" is the same as asking "How can you call God all-powerful if He cannot make a stone so heavy that He can't life it?"
Both questions belong in the category of invalid questions.
How is the question at hand invalid?
Analogy time!
I watched a thing on the Discovery Channel a while back about a huge cattle transporter ship. They mentioned some of the problems with moving cattle around in chutes.
For one thing, cattle get spooked easily, especially by glinting or moving objects. If a chain on a gate catches the light the wrong way, then a cow can be startled. For another, cows will panic if they don't have a good footing - if a slope is too steep or slippery, they'll freak out.
At best, these effects will just make the cows uneasy. At worst, they will cause the cows to stumble and get trampled. To prevent this, the cattle handlers now design their chutes with these sorts of things in mind.
Now... say you're on a cattle ranch. You've got to vaccinate the cattle; you do this by corralling them into a pen, then sending them down a chute where they get injected one at a time. This is good for the cows, because it means they'll be less likely to get sick. The cows probably don't know that the experience is good for them.
With all this in mind, which do you think is more benevolent on your part as the rancher?
- leaving the corral and chute like it always has been, because you realize that even if a few cows get spooked or even hurt, this is still outweighed by their getting vaccinated.
- removing anything from the corral and chute that would spook the cows and put a better floor on the chute, in order to minimize the discomfort the cattle feel while they're going through the process.
Asking why God can't eliminate human suffering is like asking why a rancher can't eliminate cattle discomfort. There's nothing inherently contradictory or paradoxical in the question, even if we take as given that God knows much, much more than we do.