> Anything that is reasonably possible to do by a single individual right now
Economic theories don't usually depend on the concrete specificity. Moreover; economic theories actually often pose the question "What if this thing that was not possible before suddenly becomes viable".
> divide by zero then it's a dumb theory and close to zero passing readers will take it seriously.
That might be a bad example; regular math doesn't do divide-by-zero, but we still use it very much.