It’s helpful, as with his Third Way, to begin with a metaphor, in order to get an intuitive feel for the proof.
Our perspective is supported by a rigorous and elegant metaphysical framework, which began with Plato and particularly Aristotle.
Imagine that you are an astronomer on a world with one moon. It is always night on your world, and the moon is the only body in the sky.
Every grain of sand is a link in an essential causal chain.
St. Thomas laid the intellectual groundwork for modern natural science — the absolute distinction between existence and essence.