It’s so important to have a sense of purpose that it underlies human happiness.

[newkeenlearner]

Shouldn't "it" be removed?
It’s so important to have a sense of purpose that it underlies human happiness.
Source: Longman Dictionary

 

[bubbha]

"it" refers to "sense of purpose".

 

[newkeenlearner]

"it" refers to "sense of purpose".

But we have "that", why do we need to use "it" again?

 

[emsr2d2]

We don't. In my opinion, the original is incorrect.

It's so important to have a sense of purpose that underlines human happiness.
It's important have such a strong (or other appropriate adjective) sense of purpose that it underlines human happiness.

 

[Tdol]

It's not a very comfortable sentence, but removing it changes the meaning for me. I think the original means that a sense of purpose underlies human happiness, while the version without suggests that there could be various different senses of purpose.