Possible Clues:

• "__, ergo sum"
• Start of a Descartes declaration
• Literally, "I think"
• "---, ergo sum"
• Descartes opening
• '-- ergo sum'
• Start of a line ending in a sum?
• Epistemological principle, familiarly
• 'Ergo' preceder
• Why I must be erotic, go-go dancing: to get a quantity of money