@Pete
Reminds me of a -sane - government official responding to a pestering about some imagined danger to public health/safety on Radio 4 years ago ...
After repeatedly telling the interviewer that there was no significant risk, that the risk was insignificant, that whilst it was theoretically possible the likelihood was negligible, the interviewer hit him with a perfect...
"Yes, bit it *is* possible, isn't it?" (=all Radio 4 listeners should begin/continue to panic)
To which the weary interviewee responded, patiently, but with the gentle sigh of someone seeking to reassure a child, "Almost everything is almost always a possibility."
Pause. Silence. End of interview.
The only certainty in life is death - even taxes are optional (NB, the British invented Income Tax - a "temporary measure" if I recall my history correctly - to pay for the Napoleonic wars; if we disinvented it, would the rest of the world follow again?)