Possible Clues:

• Brit remembered for his circles
• ___ diagram (logician's tool)
• Kind of diagram that the Mastercard logo resembles
• Mathematician John ____’s best-known idea was, in his own words, “representing propositions by inclusive and exclusive circles”
• Kind of diagram with overlaps
• Logician for whom math diagrams are named
• 'Symbolic Logic' author John
• John ___, English logician, best known for diagrams used in set theory
• Type of diagram
• English logician with a diagram named for him