Dressing Decently

Give me an instruction manual with clearly defined rules and I am comfortable. Something like "If he kicks you in the pants, he does not like you' and I know where I stand. The problem, though, is when things get imprecise. People, more often than not, are more like "Sometimes, he will yell at you. Sometimes, he will smile and walk away. Sometimes, you can keep talking and he will gaze over your shoulder as though he is listening to an angel blowing a trumpet in the far horizon. Any of that may mean that he does not like you. It may also mean that his mind is elsewhere. Or...". You know what I mean - imprecise!
Why individuals? Even Society is like that - and never more so than when it comes to defining decent dressing. The dratted thing seems to obey no rules. I have tried and tried to determine the rules to identify decent dressing and failed miserably.
My first assumption was that the more a dress revealed of skin acreage the more indecent it was. Applying that concept proved a failure. People wrinkled their noses at me for walking in wearing a lungi-kurta whereas the chap in shorts, showing spindly legs and knock-knees, was apparently the heights of decency. As for women, the half-sari was by far more decent than the salwar-kameez apparently though the latter concealed more than the former, since the former did leave portions of the mid-riff bare. (Tamil Nadu, ladies and gentlemen, so please do not poke in your 'indecent' North Indian ideas).
Assuming all this was merely applicable to adolescents and the rule would work much better in adulthood was also a fallacy. The first time I walked into a club wearing a round-neck disabused me of the notion that concealment was the essence of decency. "Collars! Collars!" was the cry as a man with his shirt-buttons open till the waist, revealing a chest that would rival a gorilla, walked insouciantly in, while I was stopped by a sneering security guard. Seemed to me that wearing collars without shirts was more decent than shirts without collars.
Perhaps, then, indecency constituted of WHAT was being revealed. Maybe I could derive a standard rule on that basis. I float this idea with a friend and he came out with a shocker. Apparently, at some point in time in England (Victorian age??), a woman could cut the neck of her dress to just above the nipples and still be decent. BUT, nobody would be tart enough to allow the hem of her dress to rise high enough to show her ankles. Ye Gods! If I cannot decide upon decent dressing by whether it conceals the most NOR even expect the need for the same parts of the body to be concealed - across cultures and across time in the same culture - I was sunk.
Seems to me that decency in dressing is what we decide is decent and the same shall change from time to time based on our whims and fancies. A lot of people, though, are not nimble enough to adapt to the fact that what was dressing indecently yesterday was the heights of decency today and the vice versa. No wonder they make fools of themselves by crying themselves hoarse over indecency and finding no support.
The way things are, I suppose something like this would have happened in the early days of mankind's existence.
"Do you know what Lilith has gone and done?"
"What now?"
"She is wearing leaves around her waist"
"NO! Really?"
"Yes! That tart will do anything to attract the attention of the men."
"True! Why can't she be decently nude like the rest of us."
"What next? Will she be covering her breasts too?"
"Wouldn't put it past her. Wanton hussy!"
(That, of course, with due apologies to those who KNOW that it was Eve who started it all after being inspired by eating an apple.)
Anyway, now I know that I will never get the hang of what decent dressing is all about. Will someone - PLEASE - give a detailed listing and blow the whistle on it every time there is a change?