Just like that?

When we say, "The car could have climbed to the top of the hill," we mean the car had enough power to reach the top of the hill if someone drove it there. We don't mean that on an occasion when it was parked at the bottom of the hill, the car could have just taken off and climbed to the top, instead of continuing to sit there. Something else would have had to happen differently first, like a person getting in and starting the motor. But when it comes to people, we seem to think that they can do various things they don't actually do, just like that, without anything else happening differently first. What does this mean??

Thomas Nagel - What does it all mean??, Chapter VI Does "just like that" in the context above mean "immediately"? Many thanks