The way to know it all is to change the definition of “all.” Schools do this, for example, by defining “all” to mean everything on a test. Then it’s possible for someone to know it all. Schools create the illusion that the world is finite. You may not know everything, but someone does.
The desire to know it all is pernicious. The only way to accomplish it is to shrink your world. That may be OK for a while to focus your attention. The danger is that you can succeed and forget that you started by drawing arbitrary boundaries.
When I was very young, I thought that if I read every volume of the World Book Encyclopedia, I’d know everything. Of course I wouldn’t know everything, only what the editors of the encyclopedia chose to include.
If you want to learn English by first learning all the vocabulary, you’ll never speak English. Even if you learn every word in a particular dictionary, you still haven’t learned every word in the language.
Computer languages are orders of magnitude simpler than human languages, but they’re still too complex to learn exhaustively. If you want to learn every nuance of C++ before writing programs, you’ll never write a program. And if you think this is because C++ is a large language, it’s hardly possible to understand C exhaustively either if you take into account all the subtleties of how features are actually implemented on various platforms.
A common problem in math is how to select a finite sample from an infinite space. Maybe you have a function defined at an infinite number of points and you want to approximate it by sampling it at a carefully chosen finite set of points. This is a good metaphor for life.
Even when things are finite, it’s often very practical to think of them as being infinite. (See Infinite is easier than big.) Many aspects of life are effectively infinite.
Related post: Evaluate people at their best or at their worst?