"This third objection also applies to other explanations of the forcé of morality which appeal to the interests of the person who must act. For example, it may be said that you should treat others with consideration so that they'll do the same for you. This may be sound advice, but it is valid only so far as you think what you do will affect how others treat you. It's not a reason for doing the right thing if others won't find out about it, or against doing the wrong thing if you can get away with it (like being a hit and run driver)."
[Thomas Nagel, What does it all mean?]
What is the main clause of the second if clause? thanks!