At Park Street Station, one of the oldest below-grade railways stations in the United States, the rolling stock of the Red Line slips into the belly of downtown Boston beneath the Green Line. Because of the duplexed nature of the stop, this was at one time called "Park Street Under"; its Green Line counterpart was "Park Street Over." The cars come to a stop here, but why? The epiphenomenal answer is: "the driver of the car pulls a lever which attenuates the motion of the car." The systematic answer is: "the car is compelled to stop because of a vast series of impersonalized time-tables and routines which compels all such cars to stop here, unless they are on fire or hijacked or otherwise operating nonsystematically." Both of these answers evade the truth. Look up above the cars, about a third of the way down the platform, and observe the great brass hand which silently commands the cars to HALT.