One thing humans seem to have a challenge with is being comfortable with the unknown. Waterfall project management gives one the illusion of certainty, that you can know what you are going to get and when you are going to get it at the beginning of a project. Scrum comes from the opposite direction. It asks you to admit that you don’t know at the start, but that you will learn as time goes on.

Waterfall’s illusion of certainty starts to dissipate almost as soon as it is established and generally is blown away over time. Near the end of a waterfall project there is a metric ton of anxiety and ambiguity about what exactly will be delivered and when it will actually happen.

Scrum starts out completely uncertain about what will be delivered when and sprint over sprint gets more and more certain about what can, will and should actually get done and when it is going to happen. By the end of a Scrum project, everyone is so certain it is almost anti-climactic what will happen with the final releases.

I much prefer the way Scrum learns over time what reality will be versus Waterfall’s assumption it knows everything up front. Scrum deals in reality while Waterfall deals in fantasies, which much more often than we would like to admit, never come true.