Now that's embarrassing! Sheesh! My usual proofreading skills should've caught that immediately.
Clearly, 'disprove' should read 'prove'. I'm making the change.
By the bye, technically that doesn't count as a so-called double negative, since the negative elements occur in two separate phrases. In English a double negative would look, for example, like "I don't know nothing."
A double negative, normally a no-no in English (but sometimes called for and therefore grammatical), is standard in other languages (eg, French and Russian) when the proposition must be negated.
