How do we visualize something that is a independent of experience?
How do we visualize green for example without ever seeing it? We can describe it through language but we would never have that subjective and indescribable experience of seeing green for the first time and explaining what it is after. Same goes for mathematical objects. And let's say Modular Functions which even professors have a hard time explaining. How do we even explain what a modular function is to a person who doesn't understand the language of mathematics? We can explain it in the simplest terms but will possibly stop and say it can't be explained easily. That's because we don't have the perception of a mathematician or we don't have the perception to see what green looks like. We could explain it in thousands of words and still not have the simplest clue.
I'm not really sure what the question is getting at-- the question title speaks of the a priori, yet the text of the question uses examples (like the color green) that are clearly a posteriori. And are we really speaking of "visualizing" without "seeing", or about indirect knowledge in general? Finally, is the OP actually arguing that it is impossible to teach things to people?
I really need help I've did this to the best of my ability , will someone help me?