What are the motifs in Amadeus by Peter Shaffer?

Justice and injustice is a recurring idea. As a result of what he considers to be God's injustice, Salieri decides to exact his own form of justice regarding Mozart, even though he risks damnation. A bitter Salieri warns God that he now considers him an enemy, and so with his "last breath" he will try to block God's plan for Mozart's "worldly advancement." After reading Mozart's manuscripts and appreciating the exquisite beauty of his work, Salieri confesses that !us life then acquired this "terrible and thrilling purpose" He hints at his plan to destroy Mozart when he insists that he will now engage in "a battle to the end" with God and that Mozart will be "the battleground."