Today I wrote this draft of my clothing manifesto. I have been thinking about--well, call it a philosophy of clothes, for lack of a better name--for some years, but this is the first time I've tried to write it down in an orderly way.
The first purpose of clothes is Modesty, also known as Covering Up. In Genesis, as a result of sin, people noticed they were naked and God took steps to fix this. That is why we wear clothes even in the summer, when we don’t need them temperature-wise. This is one command we still keep: clothes-wise, even our immodest culture draws the line somewhere. Thus, clothes have a moral or theological aspect. It’s not all relative. I should also point out that modesty is practical, too. Objectively, most people look better covered up. Much better.
A good outfit is, or can be, art. If it is objectively excellent, it will in some sense reflect truth and can be worship.* Clothes can have the effects of other types of art: pleasure, amusement, usefulness, and edification. I think the thought and effort that goes into a good outfit is artistic labor just as writing or sculpting.
Clothes should be appropriate for one's culture and situation. They are a tool for your objectives: if you want to deal with other humans, you should probably dress in a way that will underline your purpose, not work against it. Fashion is a factor in this. It’s not the be-all and end-all, but you really should at least be aware of what the fashion is and if you ignore it, be doing so on purpose. It’s like writing: if you want to get away with being ungrammatical, you need to know what the proper grammar is and have a good reason for not following it. Third, part of dressing appropriately is to be helpful toward the other persuasion. Attention-getting is probably not a great idea.
Clothes should be appropriate to the wearer, physically and spiritually. First, it's really important that you get your inner life right. Beauty is in “the inner person of the heart, a gentle and quiet spirit, which is precious in the sight of God.” Girls are more likely to get over-fixated on clothes than guys, in my experience, and Scriptural warnings back that up. Second, you should be aware of your coloring and body type. It doesn't bless anybody to make yourself look like you've got a horrible disease. Third, you should find out what your personality calls for. There’s no reason to ignore your tastes, and excellent reason to consult them, though they aren't everything and need to be trained in appropriate sentiment, like Lewis talked about in The Abolition of Man. But it's very depressing to see hordes of teenagers wearing ugly clothes, not because they like them, but because everyone else is wearing them!
Clothes are also useful for climate control. In the winter, one likes to avoid hypothermia. In summer, one would rather not perspire too heavily. Layers are useful techniques.
And then there are the psychological effects. A good outfit (particularly including high heels) can give the wearer confidence, make an otherwise bad day bearable, and generally spread light and happiness. This phenomenon really exists for some people. Colors and styles can also reflect one’s mood. Some days, I just don’t have the emotional energy to deal with all black and gray, for instance, or hot pink and zebra stripes. People should wear clothes they like. It just makes life nicer.*This definition of art is adapted from Ben Adams; I think it's an excellent working definition, hence my using it. :-)