Final answer:
Cotton Mather advocated for smallpox immunization while believing in witches
Step-by-step explanation:
The person who advocated to immunize citizens against smallpox, despite speaking convincingly about the existence of witches, was Cotton Mather. Cotton Mather was a prominent Puritan minister in the 17th century and played a significant role in the Salem Witch Trials. He believed in the existence of witches, but also saw the importance of immunization in preventing the spread of diseases, including smallpox.
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