[resu]

How do you explain something that has potentially unlimited inputs, and whose many inputs/actors do not act sensibly or in their best interest at all?

If you could fully explain an economic system down to the finest detail, you could more less accurately forecast all the human behavior within that system.

[ArkyBeagle]

Economics describes emergent phenomena. And widely-held beliefs about economics affects the behavior of the thing being studied. This is self-referential interaction highly amplified.