Agatha was at this time in her seventeenth year.

She had a lively perception of the foibles of others, and no reverence for her seniors, whom she thought dull, cautious, and ridiculously amenable by commonplaces.

But she was subject to the illusion which disables youth in spite of its superiority to age.

She thought herself an exception.
Crediting Mr.Jansenius and the general mob of mankind with nothing but a grovelling consciousness of some few material facts, she felt in herself an exquisite sense and all-embracing conception of nature, shared only by her favorite poets and heroes of romance and history.
Hence she was in the common youthful case of being a much better judge of other people's affairs than of her own.

At the fellow-student who adored some Henry or Augustus, not from the drivelling sentimentality which the world calls love, but because this particular Henry or Augustus was a phoenix to whom the laws that govern the relations of ordinary lads and lasses did not apply, Agatha laughed in her sleeve.
The more she saw of this weakness in her fellows, the more satisfied she was that, being forewarned, she was also forearmed against an attack of it on herself, much as if a doctor were to conclude that he could not catch smallpox because he had seen many cases of it; or as if a master mariner, knowing that many ships are wrecked in the British channel, should venture there without a pilot, thinking that he knew its perils too well to run any risk of them.