Can(not) do It

Initial Prompt:
Thrasymachus said that justice "is nothing other than the advantage of the stronger."  Do you agree?  Why or why not?
Does having the ability to do something make it morally acceptable to do that thing?  Put differently--if you can, may you?  Why or why not?

The assumption that justice can only be boiled down to the concept of the advantage of the stronger is wrong, and at the very least shallow. In the case of Thrasymachus, he is referring to justice as just. He sets an example of different rulers providing laws under their type of rule, he states that to follow these rules is justice, whether or not it is correct or incorrect as he points out that rulers makes mistakes. In my own opinion, justice is not defined by the laws created, but rather, the laws are (hopefully) created by the guidelines of justice. His situation puts forth the possibility of incorrect rulers, and that a rule made by the ruler might be incorrect, so instead of the rule being based on what is right, it is based on the power the ruler has. My disagreement runs with the assumption that the law is just already. If anything laws put down are not justice but determined later as justice once its effects are evaluated.

I think the argument of ability meaning morally acceptable is also a shallow argument. In the terms of can and may, may indicates allowance. Can on the other hand, indicates ability, but what is this ability? If you are able to do something, you are also able to not do it. So the ability to dictate actions based on ability is moot as there is ambiguity whether the action is doing it, or not doing. Therefore you cannot make a moral decision on this ambiguous rule.