Present and analyze the arguments for and against the use of atomic weapons on Japan.

For:
The dropping of the atomic bomb on Japan was essential to save the lives of Allied soldiers. Had Japan not been bombed, then it's almost certain that a land invasion would have been necessary. It has been estimated that this could have cost around half a million casualties.
It was highly unlikely that the Imperial Japanese Army would ever surrender. Right from the start of the war, the Japanese High Command had forced their men to fight to the death. In the event of an Allied land invasion, Japanese citizens were to be mobilized as part of a fanatical resistance campaign involving suicide bombers and acts of urban terrorism. Without the atomic bomb, the Allies would have been forced to fight a bloody, drawn-out campaign against domestic insurgents that would have greatly prolonged the war.
The Japanese Imperial regime and its militaristic ideology needed to be destroyed once and for all. The lessons of World War One had shown the dangers of simply concluding an armistice with a defeated power, on whatever terms. Imperialism, militarism, and emperor-worship needed to be removed for good if Japan were to be prevented from rising again. Dropping the atomic bomb allowed the Allied forces to do precisely this.
Against:
Dropping the atomic bomb on Japan was completely unnecessary. Civilian members of the Japanese government, those closest to Emperor Hirohito, were in favor of surrender, provided that the emperor's safety were guaranteed. As no such guarantees were provided by the Allies, the political position of the Japanese military was strengthened, and so Japan fought on.
The bombing of Japan was immoral as well as unnecessary. The deliberate targeting of civilians is never acceptable, whatever the situation, and the bombs dropped on Hiroshima and Nagasaki caused death and suffering on a massive scale. The Allies had earlier shown restraint in refusing to order the gas bombing of German cities unless the Germans attacked first. That was much earlier in the war. If restraint could have prevailed then, surely it could do so when the war was drawing to an end.
President Truman had the option to invite Stalin to sign the Potsdam Declaration, which would have formally committed the Soviet Union to demanding Japan's total surrender. Faced with this additional pressure so close to its territory, it's more than likely that the Japanese would soon have capitulated. Yet Truman was reluctant to get Stalin on board, because he was concerned about what demands he would make in return for his signature.