Beethoven's despairing letter that showed loss is known as what?

Beethoven's despairing letter that expressed his feelings of loss and isolation is known as the "Heiligenstadt Testament." Written in 1802, this letter was addressed to his brothers and revealed his deep struggle with deafness and the emotional turmoil it caused him. In it, he articulated his despair over his deteriorating condition and contemplated his purpose and legacy as a composer. The document is considered a significant insight into Beethoven's psyche and his determination to overcome his challenges.