It is my understanding that at the most fundamental level, a black hole is simply an object with a gravitational field so strong that there exists a sphere that lies outside the body of mass of that object from which the escape velocity is equal to the speed of light. In other words, a body of mass smaller than its Schwarzchild radius. I believe that my problem is that I am thinking about this from a perspective based on concepts of classical physics. Here is the reason for my confusion : The escape velocity from the surface of the Earth is about 11.2 km/s. However, this does not mean that an object must reach 11.2 km/s to escape the Earth's gravitational influence. As I'm sure those of you reading this know, it is simply the instantaneous velocity an object would need to escape the Earth under no further power (via free fall) after that initial instantaneous velocity was achieved from the surface. It does not prevent an object from building a ladder and climbing out the the Earth's gravitational influence at 1 m/s, or under some kind of propulsion system either at any velocity less than that escape velocity. My question is why then is it stated - time and time again - that nothing can escape a black hole? Other than the obvious things like violent tidal forces that would rip an engine (or a human) apart, what fundamental concept(s) of general relativity prevent someone from flying out of a black hole under power?