Nine Inch Nails - The Downward Spiral

How can Nine Inch Nails be so certain that it's a downward spiral? Couldn't it just as easily be an upward spiral? Surely it just depends how you approach the spiral.

My approach has always been to start at the bottom and try and work my way up. This at least gives the illusion of an upward spiral. However, I regularly slip and undo my good work by sliding back down the spiral.

Nine Inch Nails strike me as the kind of band who are wedged somewhere in the middle of the spiral, arguing about which way to go.