This week we meet Sock. Every evening Sock and various companions meet at the park to go for a walk and discourse on a variety of lofty topics.   On this particular evening, cold and blustery, it appears it will only be Sock and his faithful hound Sally. But just as they set off, a young lady appears and together the trio ambles up Lyceum Hill.   Soon talk turns to Camus' Four Conditions for Happiness. A lively discussion ensues.  But then, suddenly, this newest member of The Walking Philosopher's Club bids farewell and vanishes into thin air. Was she ever really there? Or had Sock merely conjured her up?   Does it matter? Does such a phenomenon as reality even exist? Join the walk and see what you think.See omnystudio.com/listener for privacy information.