>>Here is the dilemma: Weapons research produces in the first place not guns, bombs, bullets and planes and the various command, control and communications hardware and software needed to use these things, but plans, blueprints and designs – knowledge and know-how. Unless these useful plans are lost or destroyed, they can be implemented or instantiated many times over, and thus project unforeseen into the future.

The AK 47 design, as opposed to the individual weapons, won’t wear out; and providing the materials and skills are available, they can be made at any time in the future. The weapons design with the most longevity that I know of is the onager, the one-armed catapult used at the siege of Syracuse under the direction of Archimedes in 212 BCE and invented some centuries earlier. Aficionados still build onagers from the original plans. Now suppose that J, a weapons researcher, designs a weapon because her country is in dire threat from a wicked invader: there are many examples of this, from Archimedes to Watson-Watt the inventor of radar, and beyond. But when the emergency has passed and there is no longer just cause for using the weapon, J's invention is used in other circumstances which she does not condone, such as an unjust war. There is a moral dilemma here for the following reasons. I assume that J is a moral person and hence does not want to do harm unless she has sufficient justification. The imminent likelihood that an aggressor will destroy her family, country and way of life is surely sufficient justification. But the weapon design persists into the future, and once out of J's control can be used for unjustifiable harms. What should J do? And is this really a general problem, or one that only worries Kalashnikov?<<