What your mom said is true. Franklin is trying to say the person has to see it for themselves - what is true for you is true for you - not necessarily they need to learn from experience. I correlate this to Plato's "Shadows on the Wall" story.
I meant Plato and made the correction, sorry. Here is a reference: In the allegory, Plato likens people untutored in the Theory of Forms to prisoners chained in a cave, unable to turn their heads. All they can see is the wall of the cave. Behind them burns a fire. ... The puppeteers, who are behind the prisoners, hold up puppets that cast shadows on the wall of the cave.