Ah, no. Economics is, indeed, a science. It's just that it's not that kind of science. It's a social science, not a physical science. As such, it's laws are based on how humans act, and therefore how they think. Hence the name of the Austrian classic, Human Action. Anyone who trys to tell you that mathmatical formulas can be derived from the economic data, or that the laws of economics drive the public and not the other way around, (*cough* Keynes *cough*) is full of crap. Economics is the "dismal science" because it's a social science. Physics is easy, your experiments (above quantum) are not affected by observations. Humans don't act that way, they respond differently to the same stimuli, and moreso when they are aware that they are the experiment.
I think we're arguing about the semantics of the word
Science here, but nonetheless note that my point is that the so-called "social sciences" (amongst which Economics) are not
yet real sciences (hence why I called them
proto-sciences) because
a) it's still difficult or even impractical to conduct controlled studies on their objects of study, and
b) they're not yet properly anchored in the great chain of scientific knowledge.
And by the way, I think you have a cartoonish view of Keynes. One reason why I lean more towards Keynesianism than other schools is because it acknowledges that there is no such thing as a perfectly rational
Homo economicus. Coupled with information asymmetries in markets, this means that a pure market-lead economy will result in sub-optimal global outcomes.