A non-doer is very often a critic-that is, someone who sits back and watches doers, and then waxes philosophically about how the doers are doing. It's easy to be a critic, but being a doer requires effort, risk, and change.
Wayne W. Dyer (2009). “Staying on the Path: Easyread Super Large 20pt Edition”, p.12, ReadHowYouWant.com