| | Re: Hardly versus Barely
Hardly means "almost not" and is always negative in implication. So for example : I could hardly see anything = I could see almost nothing
Barely on the other hand means "only a bit" but is often used to emphasise the positive aspect. So : I could barely see anything = I couldn't see much but I could see a bit.
In my examples, there's not much difference in the actual situation. It's more in the speaker's perception. But if you look at your example you'll see that a positive interpretation doesn't work : the writer definitely means that it's not a new idea. It's hardly a new idea but.. = It's not really a new idea but.. You couldn't paraphrase it as "it's a bit of a new idea but...".
Think about the Phil Collins song Another Day in Paradise, which includes the line - She can't walk but she's trying. You'd probably paraphrase that as She can barely walk rather than She can hardly walk... . With the use of barely the emphasis is placed on the fact that she can walk a bit - not much but a bit. So it places the emphasis on the positive aspect and therefore matches the second part of the line but she's trying.
Hope that helps.