I'm coming at this from a scientific point of view, having had no formal training in economics - most of what I know about it was from self-studying an undergraduate economics textbook.

My question is, why do economists disagree so much? This doesn't happen in the sciences. For example, for the question "will a driver in a car with these safeguards survive a collision at 100km/h", most scientists will agree on an answer. It might be conditional on various things (e.g. age of the driver), but most scientists will come to the same conclusion.

However in economics, it's different. Faced with a question such as "should we provide more fiscal stimulus for the economy", it's possible that one big group of economists says "yes", and then another big group says "no". To some extent this might be because of personal interpretation of what is desirable. However I would expect that economists should still be able to say something like "if you provide fiscal stimulus, this will happen, and it's up to you to judge whether the consequences are desirable", and yet it seems there's no consensus on what will actually happen. It doesn't help that when I see economics debated in the media, both sides advance what looks like reasonable arguments.

Does economics have predictive power? If so, why can't economists simply *tell* policymakers what to do? If not, what's the point of economics (it might as well be astrology)?