Everyone knows 1+1=2, so why did Russell spend many many pages/hours on a proof, surely if people know it then it's easy to demonstrate? /s Programmers are not

Everyone knows 1+1=2, so why did Russell spend many many pages/hours on a proof, surely if people know it then it's easy to demonstrate? /s Programmers are notoriously good at documenting everything after all. /s It's easy to give documentary evidence for things someone found self-evident and so only wrote a scribbled note about in a workbook 40 years ago. /s FWIW patent law obviousness is not the same thing as ordinary notions of obviousness either. All my personal opinion, ofc.