As can be supported or proven by sound logical deduction, evidence, and precedent
You can use arguably when you are stating your opinion or belief, as a way of giving more authority to it. They are arguably the most important band since The Rolling Stones. used when giving your opinion to say that there are good reasons why something might be true
If you say that it is arguable that something is true, you believe that it can be supported by evidence and that many people would agree with it. It is arguable that this was not as grave a handicap as it might appear
An idea, point, or comment that is arguable is not obviously true or correct and should be questioned. It is arguable whether he ever had much control over the real economic power = debatable