Possible Clues:

• Conclusion of a Cartesian conclusion
• Words on either side of 'what'
• ''__ Sam'' (Sean Penn film)
• Nas's third studio album, after 'Illmatic' and 'It Was Written'
• "___ the eggman!"
• Sum, sometimes
• Sam ___ (Seuss character)
• Descartes' deduction
• Leonard Nimoy's '___ Not Spock'
• 'Don't you know who ___?'