“狂妄的想法”可以翻译为 “arrogant/presumptuous thought/idea”。
arrogant 意为“傲慢的,自大的”,强调过分自信且带有轻视他人的意味。
presumptuous 意为“冒失的,放肆的”,侧重于行为或想法超出合理界限,缺乏应有的谨慎。
根据语境,两者均可使用。例如:
He had an arrogant thought that he could succeed without any effort. (他有一个狂妄的想法,认为自己不费吹灰之力就能成功。)
It's presumptuous to assume we know everything. (假设我们无所不知,这是一种狂妄的想法。)