To do it for nothing?

Can you please explain to what he reffer when saying "you don't want to do it for nothing"? and nothing here means for no return? and if yes what return? (I add the video down below the relevant unclear part is from 0:44)

The reason for writing the paper was trying to show that high public debt is bad, but may not be catastrophic. So, it's not as if I want more debt, but I want to say that even if it is more debt, maybe that's not the end of the world. The second point, I think is the most relevant one - but you don't want to do it for nothing, for no reason, but if you have good things to do with it - whether it's public investment, whether it's propping upward, in a recession which I'd to zeroed out you should do it.