early 15c., "pertaining to an archetype or model," from Late Latin idealis "existing in idea," from Latin idea in the Platonic sense (see idea). Senses "conceived as perfect; existing only in idea," are from 1610s.
"(hypothetical) perfect person, thing, or state," 1796, in a translation of Kant, from ideal (adj.). Hence "standard or model of perfection" (1849).
a poem or essay may be typical of its period in idea or ideal content