I have a Windows 10 (windows 7 -> 10 upgrade) machine with 10+ years operation, Windows Defender has never caught or warned me about anything. So either:

1. I never downloaded malware

2. Windows Defender is useless and doesn't catch anything.

Also possible it was doing its job, but was useless at notifying you that it had done anything...

Why/how should he prove something that did not happen? An event, a fact can be proved... not their absence.

Try for yourself: prove your have not done [X] in the last 10 years.

You're mistaken, this situation doesn't require you to disprove a negative. The parent is claiming to have proven a negative.

They've claimed to have never gotten a virus. They have no way of knowing if this happened, as a virus isn't going to demonstrate it's presence.

So I guess the right question is "Are you sure?", not "Prove it".

I was going to write "How would you know?" and in retrospect I should have.

You prove Windows Defender will keep you virus free first

Well, you can easily find out if it's detected anything by checking it's history, as opposed to having no idea if you have any malware whatsoever - which is what you're advocating for with this stance.

Right, so check it first, and if it hasn't ever found anything, I guess you're good to disable it.

So if I’m a soldier in Ukraine, you’re suggesting I check my bullet proof flak jacket to see if there are any bullet or shrapnel impacts, and if not I should ditch it?