The Man
Unbanned zombie poster
This needs a little more discussion since there is an outside possibility, however slim, that doron may learn something. Addition provides a good example of something that works differently when we deal with the infinite. Despite dorons assertions to the contrary, mathematics doesn't assume the infinite to be a simple extension of the finite.
Addition is commutative. In computing the sum of numbers in any finite set, it does not matter what order the additions take place. Commutativity guarantees the final sum will be the same regardless. (Compare that to subtraction, which is not commutative, and you'll find the order does very much matter.)
However, the same cannot be said for the addition over infinite sets. The Man asserted the sum of all integers is 0. His statement is true, but it rests on a hidden assumption about the presumed order in which the additions are made.
Consider these two summations:
0 + (1 + -1) + (2 + -2) + (3 + -3) + ...
(1 + 0) + (2 + -1) + (3 + -2) + (4 + -3) + ...
The first reduces to 0+0+0+... while the second, 1+1+1+.... Yet, both are a summation of all the integers. Depending on how things are arranged, you can get any integer result you like as the sum of all integers, or even an infinite sum if you so prefer.
No, not actually I was not asserting an infinite series of operations or any particular order for the summation. In fact the lack of having to actually perform an infinite series of operations was part of the point. Even if you do have infinite additions of “1+1+1+....” the negatives are not done until the limit of -∞, so even an infinite series of adding ones can not exceed the already positive limit of +∞ of the set. In fact that is all the positive integers are, just an infinite series of adding ones. As the negative integers are just an infinite series of subtracting ones.
Exactly “the partial summation.”ETA: ...or no definite sum at all (meaning the partial summation oscillates).