Negation of a statement: No human can fly

Question

We have the statement: No human can fly. I know that the negation of it is: One human can fly. But i'm not sure why this is true, because it seems more logical to say that at least one human can fly. In this case I described all the other possibilites as well not only the case where only one human can fly.

Answer 1

My original answer was:

Those are both correct. In mathematics “one” means “at least one” unless prefaced by “exactly.”

Some may disagree, including the esteemed Prof. Doktor Gödel below. To me, in this context, one is synonymous with a(n), the indefinite article.

Perhaps this is evidence that one (meaning you in this context) should avoid ambiguity and use some or at least one.

Answer 2

As you mentioned, the negation is "there exists at least one human can fly", while "one human can fly" is negation of "either no human can fly or at least two humans can fly".

In general the negation "there doesn't exist any being satisfying some property P" is "there exists at least one being (in particular there may be two or three or more) satisfying property "P".

Answer 3

$\sim(\forall x\in H:\sim F(x))\iff \exists x \in H: F(x)$, where $H$ is the set of all human and $F$ the predicate "can fly". Consequently the negation is "there is a human who can fly".