When a Harvard natural language parser was given this phrase in the 1960s it identified the following five parse trees in reponse.
  1. Time proceeds as quickly as an arrow proceeds.
  2. Measure the speed of flies in the same way that you measure the speed of an arrow.
  3. Measure the speed of flies in the same way that an arrow measures the speed of flies.
  4. Measure the speed of flies that resemble an arrow.
  5. Flies of a particular kind, i.e. time-flies, are fond of an arrow.
Note that the parser was smart enough to not assume the following. Either it was lexically coded to understand this as an impossibility, or it just wasn't thorough enough.

Time, an abstract concept can not perform concrete actions.

  • Time flies through the air in the same manner that arrows do.