Both Uses of

chimera
in
The Idiot

It would have been inconsistent with her character if in these visits she had been pursuing a chimera; her project was not chimerical at all; she was building on a firm basis—on her knowledge of the character of the Epanchin family, especially Aglaya, whom she studied closely.†
Chpt 4.1 *

It would have been inconsistent with her character if in these visits she had been pursuing a chimera; her project was not chimerical at all; she was building on a firm basis—on her knowledge of the character of the Epanchin family, especially Aglaya, whom she studied closely.†
Chpt 4.1

Definitions:

(1) (chimera)
a wild, unrealistic idea or hope; or a mythical creature made from parts of different animals
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

As a proper noun Chimera refers to a fire-breathing monster in Greek mythology. It is a female monster with a lion's head, a goat's body, and a serpent's tail.

More rarely, in biology, a chimera is an organism that contains cells or tissues with a different genotype.

Chimaera is also an acceptable spelling and the name of a type of fish.