What Aspect of Photography is Most Important?

There are many aspects of photography that work together to form a good image. If any of these aspects are left out of the picture, you may end up with a sub-optimal photograph. They're all important, but I'm curious which of those aspects are most important — if you had to pick only one, which would it be? As always, feel free to add answers if they're not listed here.

What Aspect of Photography is Most Important?

Last week's poll (What Post-Processing Software Do You Use?) shows that a majority of the Epic Edits readers use some form of Photoshop — 49 of 84 votes, or 58%. This is good news for me, because I won't feel so bad for speaking Photoshop terminology during my tutorials.