Peter Shaffer's Amadeus as a further expression of twinship conflict

In Peter Shaffer's Amadeus, which has much of a thematic and symbolic nature in common with its forerunners, Equus and The Royal Hunt of the Sun, stemming genetically from the unique sibling rivalry of twinship, there is more pronounced emphasis on the influence of envy and vengeance on human behavior than in the other two plays. It is postulated that the success of Equus and its implications pertinent to the competitive aspect of the relationship with his twin brother stirred appreciable intrapsychic turmoil in Shaffer and was a decisive motivating factor in his writing of Amadeus.