quixotic

他怀着堂吉诃德式的理想，试图独自改变整个社会的现状。

With his ___quixotic ideals, he tried to change the whole society by himself.

她拯救所有流浪猫的唐吉诃德式想法虽然感人，但很不现实。

Her ___quixotic dream of rescuing every stray cat was touching but unrealistic.