Ethics of Scientific Research - Second question

Are the participants of the Manhattan Project morally responsible, partially responsible, or not at all responsible for the effects of the atomic bomb?

In order to determine whether the participants of the Manhattan Project were in any way responsible for the effects of the bomb, we need to provide some definitions. By participant, we mean the scientists and researchers involved in the research and development of the atomic bomb, and not the military or political leadership involved in the project. We also need to restrict the effects of the atomic bomb to the human toll resulting from dropping the nuclear devices on Hiroshima and Nagasaki, both immediate and long term. With those definitions and qualifiers in place, the participants were not morally responsible for the effects of the bomb.
The moral responsibilities of scientists are no greater than those of the rest of society, and given the context and limitations of their research responsibilities, their moral responsibilities are limited to the decisions and course of actions available to them. Scientists and researchers are presumed to be autonomous moral agents, responsible for their own rational choices. The decision to deploy the nuclear weapon was not in the realm of responsibility of the participants of the project. The military and political leaders bear the responsibility for using the weapon on the city of Hiroshima and 3 days later on Nagasaki. However, those leaders would not have had the opportunity to use the bomb if the participants had not designed and built the device. So how far does the chain of responsibility extend?
As stated above, the moral responsibilities of the participants need to be examined in the context of the actions and decisions available to them. Examining their decision to continue the design and development of the bomb after VE day should be weighed against their holding to general moral principles. VE day celebrated the removal of the initial political reason for the development of the bomb. That political reason was officially tied to the threat posed by the prospective development of nuclear weapons by Nazi Germany.
In terms of the participant’s employment duties, the participants can be shown to generally follow the principles of non-malfeasance, beneficence, autonomy and justice. In the context of the Second World War, the researchers did not inflict unjustified harm. In fact, the direct actions and decisions made by the participants did not cause any immediate nor foreseen harm beyond that expected in war. The participants acted in a way that indicates that they intended to benefit not only society, but also science, given the limitation of what intelligence they possessed about the war situation. Along those lines, they also worked to promote justice in the world, by doing their best to contribute to a device that they believed would be used to bring the war to a rapid end. Lastly, they provided information and knowledge to the supposed rational individuals who would make the ultimate decision to deploy the destructive power of the weapon they designed and built. By continuing in their work, they did not deprive the individuals that they worked for of the autonomy to make their own informed and presumably responsible decisions.
Much can be said about the principle of autonomy. If the Manhattan Project participants had stopped their work, they would have deprived the military and political leaders of their autonomy to make a responsible decision. Another set of scientists also designed and built a different form of weapon of mass destruction, which fortunately had not been deployed in the war. The researchers who refined nerve agents and other deadly chemical weapons did not deprive their superiors of the autonomy to make responsible decisions. The rational choice made by the leaders was to not use those weapons, and there was no expectation that those same leaders would not make a rational choice with the atomic bomb. The chain of responsibility extends only to those that made the decision to use the bomb, to those that used the information and technology provided to them to cause actual harm, destruction and death.