Possible Clues:

• A leader of monks, I inferred
• American's capital conviction earlier, one not needing evidence
• Postulated after Apr 9 to King of Ireland
• A leader of monks, I deduced
• A religious leader -- one arguing from known facts
• Involving logic only (2 words)
• Derived by logic, not from observed facts
• Friar in midst of praise, it may be deduced
• Fully inferable
• Boris sheds clothes on foolish date, as we may deduce