[strken]

That's not a reply to what I wrote. I agree that preventative measures against the spread of disease include wearing a mask in public and that this is a good idea if you've got a cold, but I think that because of an assessment of the risk.

Do you need to wear a mask alone in your own garden? It could still help you avoid a possible death. The only thing that changes between "in public" and "in my garden" is the risk: the consequence is always death. Your four-quadrant thought experiment is meaningless unless you intend to suggest that any risk of death, no matter how minor, justifies an inconvenience that might prevent it.

Frankly, yes, you should look at a daily weather report before carting an umbrella around. If there's a 0.0001% chance of rain then it's okay to risk it.