Probability: How AI Deals With Uncertainty

Your spam filter does not know if an email is spam. It cannot know for certain. Nobody can. The word "free" appears in legitimate emails. The word "urgent" appears in real emergencies. No single signal is definitive. So the spam filter does not try to be certain. Instead it asks a different question entirely. Given everything I can see about this email, how likely is it to be spam? If the answer is 94%, it goes to junk. If it is 23%, it goes to your inbox. The decision is made under uncertainty,