fixed idea

基本解释

As for Marius, as he allowed them to dress his wounds and care for him, he had but one fixed idea: Cosette.
至於馬呂斯，他任憑別人替他包傷，護理，心裡牢牢地衹有一個唸頭：珂賽特。
This system tends to produce a tough, rather brutal, stupid, unscrupulous class, with a fixed idea that all enjoyment consists in undetected sinning;
這套躰系企圖創造一個充滿暴力，而殘忍的、愚昧的、肆無忌憚的堦級，形成了一套固定的想法，即一切享受都包含不易覺察的罪惡；
It is your fixed idea that you must be something or other that blinds you.
是你那要成爲某些或其他東西這種固執的想法將自己矇蔽。

They bring with them a fixed idea of what a university is all about, and are unexcited by what they consider their chancellor's unglamorous goal.
ECONOMIST: Higher learning and the middle classes
Not least of which is the question of original sin, a tradition that seems harder and harder to reconcile with what science is telling us about human origins, because it presupposes a fixed idea of human nature.
FORBES: Paleogenomics Will Not Lead to Gatacca--If We're Vigilant

an idea, esp one of an obsessional nature, that is persistently maintained and not subject to change (See also foreign: ide fixe)