No ounce of understanding, true understanding, about the depth of something or someone, is gained without prior knowledge of that person or thing.
Without knowing my husband as intimately as I do, I could never hope to understand him. Not truly. I could form some image of him based on my own desires of what I wish he were, but it would be only an illusion. And while illusion can feel very real if meditated upon and given immense amounts of energy, it doesn't make it actually real.
I could swear up and down that I know him to the tips of his toes if I had built him only within my own mind, never set a hand upon him, never touched him, never let him speak for himself. I would know every crevice of his imaginary body, every turn of his imaginary moods, and every inflection of his imaginary voice. I would understand his every whim if he were merely a construct, a reflection, of my own whims.
But, in reality, understanding my husband comes only through knowledge, through learning, through interaction and observation.