Increasingly we seem to exist in an age when the inferences of an antonym in language is far better understood, comprehended, followed than the original form. The concept of unfaithfulness is wholly construed, faithfulness not so much, impropriety occasionally expounded, propriety hardly ever, immorality somehow fully comprehended, morality a vague, arcane, Delphic, and esoteric condition. It could be argued that a negative connotation adds an element of clarity, that an unprefaced noun somehow lacks easy definition.
Everyday language, conversation has become fixated upon the physical, devolving to a construct for the indicating, explaining, describing activities and events. Overtly unnecessarily labeling, classifying the obvious, soliloquizing the boring and mundane, producing voluminous poetry and prose pandering to the bland and repetitious. Having spent unholy amounts of time polishing communication to a pristine and exact manner of addressing science, philosophy and emotional and amorous turmoil, we have within, but a few decades retreated verbally to the equivalence of stone age cave dwellers grunting back and forth with an occasional interposed belch or worse.
The modernist failure to grasp the deeper, more philosophic inferences of words removes from out vocabulary the connection between speech and emotion, the difference betwixt concept and proclivity, possibility, and fait accompli. So it is impossible to understand that being immoral might suggest the participation in something considered a socially sinful behavior yet being moral does not automatically proclaim a sinless existence, rather suggesting a credo to proactively seek a socially thoughtful, conservative, and innocent lifestyle. The one denotes physical desire, unrestraint, and probable fallibility, the other a philosophical position and fervent hope, the former base in nature, the later decidedly spiritual..
The base/spiritual dynamic applies to many a prefixed noun, faithful and unfaithful, clean, and unclean, propriety and impropriety, ad nauseum. This loss of subtlety, nuance, fineness in linguistics and comprehension has done human kind a great disservice.