idealistic adj.

"one who represents things in an ideal form," 1829, from ideal + -ist. Earlier (1796) in a philosophical sense "one who believes reality consists only in (Platonic) ideals" (see idealism).

It seems even incredible, that any Idealist in any age could forget himself so far as to run his head against a post, merely because he found in his system, that no external world does exist, and that therefore nothing could be without to hurt him. [F.A. Nitsch, "A General and Introductory View of Professor Kant's Principles," 1796]

Earlier still, "one who holds doctrines of philosophical idealism" (1701).

Middle English -ik, -ick, word-forming element making adjectives, "having to do with, having the nature of, being, made of, caused by, similar to," from French -ique and directly from Latin -icus or from cognate Greek -ikos "in the manner of; pertaining to." From PIE adjective suffix *-(i)ko, which also yielded Slavic -isku, adjectival suffix indicating origin, the source of the -sky (Russian -skii) in many surnames. In chemistry, indicating a higher valence than names in -ous (first in benzoic, 1791).

In Middle English and after often spelled -ick, -ike, -ique. Variant forms in -ick (critick, ethick) were common in early Modern English and survived in English dictionaries into early 19c. This spelling was supported by Johnson but opposed by Webster, who prevailed.