In essence the principle says that not having the evidence that something might be a problem is not a reason for not taking action as if it were a problem.
It’s a very famous triple-negative phrase that effectively says that action without evidence is justified. It requires imagining what the worst might be and then applying that imagination upon the worst evidence that currently exists.
But, once you start imagining what could happen, then there is no limit. It’s a shift from the scientific ‘what is’ evidence-based decision making to this speculative, imaginary ‘what if’ based worst-case scenario.
Director International Centre for Security Analysis