Idealism is living by high principles rather than by what works. Youthful idealism, lose your idealism, principled idealism.
It is used admiringly and dismissively at once — idealism is what people are said to lose, which frames it as something young. In international relations, idealism is the school holding that values should shape policy, against realism. In philosophy it is the position that reality is mental. Note idealist; and that the word was coined in 1796, the same year as ideology.
1nounidealismLiving by high principles rather than by what works.
“His youthful idealism faded after years of working in politics.”
idealism is a guiding outlook.
Ideal plus -ism, first attested in 1796. Ideal comes from Latin idea, from Greek idea, a form or pattern.
Latin
ideālis — existing in idea
French
idéal
English
ideal
English, today
idealism
First attested 1796, from ideal + ism. ideal comes from French idéal, from Latin ideālis (“existing in idea”), by surface analysis, idea + -al, from Latin idea (“idea”); see idea. In mathematics, the noun ring theory sense was first introduced by German mathematician Richard Dedekind in his 1871 edition of a text on number theory. The concept was quickly expanded to ring theory and later generalised to order theory. The set theory and Lie theory senses can be regarded as applications of the order theory sense.
Etymology from Wiktionary, CC BY-SA