Possible Clues:

• What Mr. Spock is not
• Serving American in pub one litre at first is not reasonable
• Old soldier in trouble about line lacking sense
• Unreasonable
• Senseless, self-inflicted problem, one dividing two US states
• Unsound
• Having no base in Paris he meets soldier in pub
• It's beyond the bounds of possibilities unit lost sound
• I left American soldier in pub not making sense
• It does not stand to reason that I will go back to start with