I hear this a lot, and when phrased like this, it is an assertion and not an explanation or proof, making these empty words.
Instead we should say, “it is not physically realizable because”:
- It takes more energy than a nuclear power plant or hydroelectric dam, and you aren’t willing to pay for a massive bank of capacitors
- The size, weight, and power constraints are too restrictive (and if known which one of these is the worst)
- Forces like rust, hurricanes, insufficient attachment to ground/soil/bedrock, will cause it to fail
- The tolerable damage threshold in the operational environment is too low to be economically effective
- The required precision will take billions of dollars worth of semiconductor fab or similar apparatus
Instead we should say, “it is not going to happen in the required schedule because”:
- The manpower requirement is so extreme that mechanically moving this number of troops is even worse than D-Day or any other significant amphibious operation (you do not have enough vessels of any type, etc.)
- Even if you had all available mechanical tooling and staff at 24×7 tasking, you still can’t produce enough units (the “nine months for one baby” problem) (and its related problem of “starting more lines is too expensive”)
- The knowledge and training requirement of even a cut-down curriculum will take too long (if you have run a crash program before) to train the necessary individuals
Instead we should say, “It does not economically improve the objective”:
- We could allocate more resources to produce and supply tanks, but we would have to give up food production that is more critically needed
- We could force people to work on our dangerous production lines, but the loss of lives and health would not be worth the enhanced productivity or gains elsewhere
- We could choose to ban automobiles in this area due to congestion delays, but we have no way to get the required number of people and goods in and out in an amount of time that improves over the current gridlock
Instead we should say, “It is not compatible with our other operating requirements”:
- We could force people to do this, but it would require us to create the equivalent of a police/prison state, to monitor and limit their behavior at this granularity
- We could choose this lower standard of proof, but we would be wrongly convicting too many people (and you should say what that acceptable is, e.g. 1%, and why)
- We could choose to operate this smelter without scrubbers, but we will turn the surrounding area into a wasteland and poison our workforce
- We could choose to grow these crops here, but we will exhaust an aquifer and divert water for not much benefit
And of course we should say “our available measures to improve this are not economically profitable” or “not helping enough to justify the additional cost”.
We should recognize the classes of impossibility, according to their class of phenomenon:
- If it’s not physically possible, it’s not possible.
- If the time it takes to transport/build/learn/train is too long, it can’t be done in the schedule.
- It is possible to perform the proposed action, but due to other consequences of the action, you can’t improve on your goal this way.
- It is possible but you wouldn’t want to do that because you give up something else you want.
- It is physically possible but not economically justified.
We should not say:
- We can’t militarily defeat them, when you have the physical means (like nuclear weapons) that have been demonstrated to defeat much larger threats, in far less time.
- We can’t provide this additional education, when you have the taxation authority and overall flexibility to redirect resources.
- We can’t have our professional staff work overtime to complete this task in the schedule, when you have the money available to implement a different staffing approach e.g. than the long-run never-rich but always comfortable compensation offering.
- We can’t clean this up, when you have plenty of prison labor and are handing out welfare to half of your population that could be supplying protective kit.