He stuck to his principles.
資本主義は多くの国で採用されている。
Capitalism is adopted in many countries.
He stuck firmly to his pacifist principles until the end.
That action goes against my principles.
She never compromises her principles.
主義 names a specific stance or -ism (e.g. 資本主義), whereas イデオロギー refers more generally to the whole belief system underlying such stances.
主義 names a codified doctrine or -ism (e.g. 資本主義), while 理念 is a broader, less rigid guiding ideal.
主義 refers to a systematized doctrine or -ism (e.g. individualism), while 信念 is a personal conviction that need not form a formal system.
feudalism
exclusivism; exclusionism