Is is reasonable to believe, that an event can only be presumed to be impossible if you can honestly apply a probability of 0% to such and event?

If this is reasonable, then a Reasonable Person must have doubt about any proposition, for which any alternative proposition has a rigorously calculated probability of greater than 0%.

Does this not mean that, from a Reasonable Person's view point, using scientific method (as I presume this to be the most rigorous form of enquiry into events that we posses.), any proposition not using the limitation 'Always occurs' is not beyond reasonable doubt, (using the definition of 'reasonable doubt' as being doubt of a 'reasonable person")?