Can anyone provide the source of this quote?

I recall a quote that I want to use and I believe it is from one of Rand’s books, but I am not sure. I believe it is something like:

To say “Who am I to know?” is to say “Who am I to exist?”.

Can anyone place this quote?

Here (the last sentence of the first paragraph) is the quote you’re looking for.

When a man declares: ‘Who am I to know?’—he is declaring: “Who am I to live?” Galt’s Speech, Atlas Shrugged, P.1018

I recall a quote that I want to use and I believe it is from one of Rand’s books, but I am not sure. I believe it is something like:

Can anyone place this quote?

When a man declares: ‘Who am I to know?’—he is declaring: ‘Who am I to live?’

Thanks. I felt it was somewhere in Atlas Shrugged.