The problem is pike: br someone dropped br a pair in the lake, br and these savage predators br are multiplying, br eating all the other fish, br whose natural habitat this is. br br Your mind is a vast, vast net. br You throw it and its resources br into the lake br to try to surround all the pike. br br If you leave even two br they'll infest the whole place again. br Then you'll cast your net once more, br br maybe a bigger net, br to try to get it around br the whole problem br once and for all. br br It's hard to tell, each time— br you can boast of success at first. br br Sooner or later, though, br it will be obvious to all: br the pike will be gone, br or only pike will remain.