King Milinda was a Greek and an experienced soldier who thought he knew a chariot when he saw one. But Nagasena demonstrated that if Milinda's chariot were gradually dismantled - knock a spoke out of a wheel here, a plank off there, then a bit of the frame and so on - there was no way for Milinda to decide at exactly what step in the procedure he should stop imputing 'vehicle' and start imputing 'heap of firewood'.
Nagasena said this was because the chariot had no power to define itself from its own side. Nor was there any ideal chariot form 'in the sky' which engaged and disengaged with the timber at definite stages of assembly and disassembly. Milinda's mind was the only thing that could make the distinction between vehicle and firewood. And there were no logical rules, stepwise procedures or decision trees for Milinda to decide when to cease imputing one thing and impute another.
As with chariots, so with cars. Everyone knows what a car is. A car is an assembly of parts. But what makes those parts into a car is surprisingly difficult to pin down. At what stage on the production line do the components finally become a car? Does it temporarily cease to be a car when it's in for repairs and the gearbox is several yards away from the rest of the vehicle? Is my car still a car when I wake up one morning to find it supported on bricks with the wheels missing?
Or, could I say that the essential feature of a car is that it performs the functions of a car? So does it cease to be a car when it won't start? And does it return to the state of being a car when I cure the problem by spraying the electrics with moisture repellent? Does the true essence of being a car therefore reside in an aerosol can?