/ aɪˈdiːəlɪzəm; NAmE / noun [ U ]
1.
the belief that a perfect life, situation, etc. can be achieved, even when this is not very likely :
He was full of youthful idealism.
2.
( philosophy ) the belief that our ideas are the only things that are real and that we can know about
—compare materialism , realism
► ideal·ist noun :
He's too much of an idealist for this government.
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WORD ORIGIN
late 18th cent. (as a philosophical term): from French idéalisme or German Idealismus , from late Latin idealis , via Latin from Greek idea form, pattern, from the base of idein to see.