Sentence:  For surely, sir, you will not assert, that a duty can be binding which is not founded on reason? If, indeed, this be their destination, arguments may be drawn from reason; and thus <WSD>augustly</WSD> supported, the more understanding women acquire, the more they will be attached to their duty, comprehending it ... 
Meaning of the word marked with <WSD> tags:  In an august or awe-inspiring manner.