idealism

Short definition from Wiktionary

Noun

1. 1
   The property of a person of having high ideals that are usually unrealizable or at odds with practical life.
2. 2
   The practice or habit of giving or attributing ideal form or character to things; treatment of things in art or literature according to ideal standards or patterns;—opposed to realism.
3. 3
   An approach to philosophical enquiry, which asserts that direct and immediate knowledge can only be had of ideas or mental pictures.