For better or worse, I treat economics as a science, and judge an economic theory on its ability to make accurate
predictions, not retrodictions. My point about "looking out the window" is that while we've been operating on a supposedly Keynesian theory in trying to repair our economy these past six years, it has consipicuously, repeatedly, and grossly failed to correctly predict the results of its own massive interventions. You don't need fancy economic theories to see how it has failed, you need merely open your eyes and look around. (And I include newspapers and television, etc, in the looking around, so my point is that it is easy to see the failures, not that it's failing literally right outside my window.) You need fancy economic theories to explain how even though the results are awful, we're still doing the right things even so.
Keynesians cover this by claiming it would have been even worse without the near-continuous and now open-ended "stimulus". I don't believe them. Had they said in advance that the current scenario was a significant possibility, I would at least listen, but instead we've been in a world where "recovery is just around the corner" for about four years now. It isn't, it hasn't been, and it continues not to be. I find it a valid theory that Keynesianism is the reason why, rather than the thing saving us. The fact that we're talking about a "new normal" is also code for "Keynesianism is a failure of an economic theory, but rather than give up the theory because we like it too much, we're going to tell people to just get used to being poorer."
(Of course if you want to say that our politicians are only using the name of Keynes for a cover while in fact not acting particularly Keynesian, well, I beat you to it. Keynesianism isn't, really. But nobody seems to open with that defense, only use it as a fallback when attacked. It's true enough in theory, but a useless defense of the theory's current users, which are what I'm actually critical of. The real Keynes is a great deal smarter than the psuedo-Keynes being used to drive policy today, but also a great deal less influential.)