Yes, that is a great idea but imagine writing unit tests for your code. Imagine someone is reading the tests as you write them (and has people whispering in you

Yes, that is a great idea but imagine writing unit tests for your code. Imagine someone is reading the tests as you write them (and has people whispering in your ears to influence what you write). Now, these people are trying to find edge cases. Remember that they just need one good edge case to pwn your code. Will you start writing more unit tests? Will your tests get more elaborate? My abstraction is bad because it doesn't cover another issue: public policy through taxation. We encourage things we consider "good" using taxes and we discourage things we consider "bad" using taxes as well. A lot of people support tax "relief" for things like mortgage loans, education loans, dependents and so on. If we want to simplify the tax code, these deductions must go away.