I want to know the answer to the following question:
What concept was relevant to the solvability of the problem of measure?
All the background I'm provided with is that "Von Neumann's work argued that the "problem is essentially group-theoretic in character, and that, in particular, for the solvability of the problem of measure the ordinary algebraic concept of solvability of a group is relevant.". Is that enough to answer the question?
Answer: yes