She said she was optimistic because people with autism have a toughness that others lack.

I was dubious, for Aunt Jane's illusions have a toughness in striking contrast to the uncertain nature of her ideas in general.

She had a toughness that did not so much beg for admiration as command it.

"More than once, I 've said to Cupcake, he can't be the milksop he seems to be, 'cause his books have a toughness in them."