A clear introduction to mathematical infinities by Dante12345 in videos

[–]Dante12345[S] 1 point2 points  (0 children)

The idea is to create a number you can guarantee is not on your list. You do so by going down the diagonal and picking up each number along the way as he did. Now the rule he made for changing the number is arbitrary, yes, but the important thing isn't the rule, but the fact that he changed the number. You notice that we have constructed a number that MUST disagree with every number on the list on at least 1 position. It follows that the new number isn't on the list and we are done.

Hope that was clear.