There's a back-and-forth email correspondence between Sam Harris and Noam Chomsky discussing ethics here. In one of the emails Sam says to Noam:
I trust that certain of your acolytes would love to see the master in
high dudgeon—believing, as you seem to, that you are in the process of
mopping the floor with me—but the truth is that your emotions are
getting the better of you. I’d rather you not look like the dog who
caught the car.
I've found only one site online that gives a meaning of it:
n. A person who has reached their goal but doesn’t know what to do
next.Notes
This idiom is based on the strange habit that some dogs have
of chasing cars that are passing by on a nearby road. What on earth
would one of these crazed canines do if it actually caught a car? This
idiom is also seen as the dog that caught the truck (1993) and the dog
that caught the bus (1994).
Wordspy
However this meaning doesn't make sense to me in the context. Sam is accusing Noam of being belligerent and cantankerous, and I don't see this as Sam telling Noam that he'd hate to see him be "the one who has achieved his goal and now doesn't know what to do."
I also found some user definitions on Yahoo Answers, but the meanings vary. The top answer there is:
the impossible has been accomplished.
The second answer is:
It can be taken two ways .
One…….it means you finally did something, you have tried many
times and failed………..or it can be a euphemism, for………the Dog is dead.
Because the dog actually CATCHING the car…..usually doesn't end well
for the dog.
Achieving the impossible doesn't seem to fit in the Harris-Chomsky discussion.
However, the dog being dead makes a bit more sense, as Sam is telling Noam that his manifest aggressiveness is not making him look good in front of their readers, and so the dog being dead could be figurative for Noam's attacks backfiring on him and making him look bad.
I'm having trouble knowing what is meant by this in the email exchange, and also in general. Stephen Colbert seems to use it in the way Wordspy defined it:
Stephen Colbert likens Trump team to the dog that caught the car
Trump and his team, he continued, are “like a dog who spent his whole
life chasing a car — now he has to drive the car.”
Entertainment
Weekly article
Does this most generally mean what Wordspy says? Also, is my reading of Sam Harris' use of it to mean "dead dog" right?
Best Answer
Maybe some people use it to mean "a goal was attained and now they don't know what to do", but in this context Harris isn't saying that. He's saying that a dubious or worthless goal was attained, regardless of what happens next.
If you race your friend to a chain-link fence and you win, only to find out the fence was electrified, you're the dog who caught the car.
For the dog analogy, either it dies or nobody in the car is concerned. The dog's aggressive attempt to achieve "catching" the car is a miscalculation. There is zero intent to convey a goal or achievement was reached, because the goal was to attack the car which is the silliness implied in the statement. The "dog" is looking for a fight it doesn't know it cannot win.
You can infer a "what now?" effect, but the gist is, it's playing out of its league and doesn't know it.