The subject of clutter is more complicated than you might think. The word "clutter" has a negative connotation - no one wants to admit they cultivate clutter, although some "Clutter Bugs" (like me) say, "My house may be cluttered, but it's not dirty." When you begin to deconstruct clutter, you find it is not simply a case of having too much good stuff and not enough space to properly store it (although that may be one aspect).
When you really get into it, clutter raises issues about all kinds of things like:
Deprivation or Disaster Mentality: "I can't get rid of this or that because I might need it some day" - "There might be a disaster and this or that will come in handy," or, "My parents who survived the Depression taught me to hoard and save things because 'You never know.'"
Materialism: Good old-fashioned Capitalism thrives on convincing us to buy more to satisfy any momentary whim or urge. Buying something to cheer yourself up is often seen as a fix for uncomfortable feelings of boredom or depression, basically to salve any wound. "More is better," is truly an American motto.
Sentimentality: Many of us are trained not only to buy souvenirs, but to hold onto them for life, along with all kinds of other mementos (old love letters, match books, pictures, stuff we "used to like," etc.)
Delusional Thinking: "I can't get rid of this - it's perfectly good - it only has (fill in the blank - one spot, or one hole, or one missing part)."
Feng Shui is the ancient Chinese art of environmental energy awareness. According to principles of Feng Shui, clutter is considered to block the flow of chi (essential energy). Feng Shui is a multi-dimensional, multi-faceted art, which deals with all levels of consciousness (the physical/material realm, the emotional realm, the mental/intellectual realm, as well as the group/collective realm).
Clutter impacts us at all of these levels. For instance, it is physically uncomfortable to live amongst clutter. Clutter assaults the senses. It is mentally and emotionally taxing to live with clutter ("Where did I put the car keys?" "Where are my clean socks?" "Where is that important paper I need right now?"). Clutter impacts spirituality by creating disturbing emotional or mental states, such as frustration, anger, or fear. I believe many people who suffer from depression could help themselves, greatly, by simply clearing clutter.
Clearing clutter can be wonderfully cathartic. The act of cleaning a closet, for instance, brings things to the surface to allow processing, acceptance, and letting go. You become lighter as your life without clutter becomes lighter.
Broken stuff, junk mail, paperwork, files, old clothes, souvenirs, books, magazines, newspapers, old electronics, cords, knick-knacks, business cards, collections, dried flowers, stuffed animals, broken pens & pencils, etc., etc.