I wish I had spent some more time expanding on that statement: maybe I'll go back and edit the entry, because honesty & compassion are only one source (although ultimately the strongest source) of strength in the book. Elana and her friends spend most of the book squared off against people who derive their strength from other sources.

I don't have the book on hand at the moment, but there's a wonderful quote where Elana talks about Commander Feric, her interrogator, who has hitherto believed that the only source of strength is fear - and now that he's seen how strong she is, he's starting to suspect that he must be afraid of her. Because he can't conceptualize a relationship with any other basis.

Or the part near the end, which I don't want to spoil, where Elana agonizes about her secret depending on a strength she doesn't have...