near-deaf. It got worse as he aged but he could generally hear himself if he listened closely (especially for his earlier works), which is why he was always awkwardly bent over the instrument. and wouldn't that just show that music theory is just as (if not more) important than going by ear? Because your analogy was going the opposite way...
From http://www.todayifoundout.com/index....rote-music-2/:
"All of Beethoven’s achievements above were done—as far as we can tell—with quite good hearing. This soon changed. Starting around 1796, we have references of Beethoven mentioning in letters hearing “buzzing noises,” but it wouldn’t be until 1801 when we have documented evidence that he had been gradually going deaf."