Watch Art Cashin: Why stock rally may not be for real

90 Seconds with Art Cashin: The 'rationality put'

Art Cashin says stocks are rallying today after hawkish Larry Summers withdrew his name from consideration to be Federal Reserve chairman and as Syria fears fade.

But Cashin, UBS' director of floor operations at the NYSE, told CNBC's Bob Pisani around midday that he'd like to see much more volume attached to the rally.

"The volume is not really living up to this move, so this is kind of exploding into a vacuum."