Even much stronger mortals than Fred Vincy hold half their rectitude in the mind of the being they love best. “The theatre of all my actions is fallen,” said an antique personage when his chief friend was dead; and they are fortunate who get a theatre where the audience demands their best.
This is a big theme in "Middlemarch": we crave to see others ideally and to be seen ideally; we suffer when we over-estimate, but also when we under-estimate.
Fred craves for Mary to believe in him.
Dorothea believes both in Ladislaw and in Lydgate when each man is disprized by others, and it means the world to both of them.
Ladislaw finds life-energies and real purpose in valuing Dorothea not only justifiably as the good woman she is but as the very ideal of woman. Dante’s love for Beatrice is subtly compared to this.
Dorothea's esteem of Ladislaw does the same for her. The misunderstanding caused by Rosamond devastates her by destroying her belief in him; and he feels equally devastated that she no longer can cherish him as good.
Dorothea's admiration of Casaubon is the most extended and famous of these
idealizations. It is a tragic over-estimation, and notably, unlike all the other instances of believing in someone, it does nothing positive for Casaubon; it does not lift him or bring out his best.
Casaubon, of course, idealizes Dorothea, but in a decidedly limiting manner, needing her to be nothing more than a compliant wife with whom he will share nothing. For Dorothea this is a living death.
Similarly, the mutual illusions held by Lydgate and Rosamond come crashing down without unlocking potential or energies, in fact by doing quite the opposite.
