Rise the question:Is learning possible
learning frome D(to infer something outside D) is doomed if any “unknown” f can happen.
Because the law learned from inside D would probably show nothing of the law of outside D.
Probability to the Rescue
According to Hoeffding’s Inequality,if large N,can probably infer
unknown u by known v.
Connection to Learning
verification possilbe if \])
Connection to Real Learning
the sum probability of all kinds of hypothesis
learning possible if 
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