What is the meaning behind the third movement of Beethoven's String Quartet No. 15, Op. 132?

It is a thanksgiving song from a survivor, titled ‘Heiliger Dankgesang eines Genesenen an die Gottheit, in der lydischen Tonart’ — Holy song of thanksgiving of a convalescent to the Deity, in the Lydian mode. Beethoven wrote it after recovering from a serious intestinal illness.