A proof (visual or otherwise) shows "how" some statement is true, as in how it is built by the preceding truths. But I always wanted to know "why" something is true. For example, a biological cell grows and division happens. I could find tons of literature which talks about "how" this happens, but not "why" this happens. What's the motivation or goal? And why that goal is pursued? What is the force behind seeking of that goal?