[solistice]

So you can't see the matrix? Take the red pill (No, that's not Modafil painted red) Neo.

On a more serious note, when do you understand something? For me, it is when I can visualize how the parts of the function interact with each other, for example for Summation, how many little functions (those functions are visual images too) in a long finite line stack on top of each other and create a large something, that might get fed into something else.