The natural world has a goal-directedness to it. There is an element of purpose. This is what is meant by the word “teleological,” a word used by philosophers for centuries to describe the apparent purposefulness of material things.
Getting to a full understanding of teleology takes some ramping up in the form of understanding Aristotle’s final causes, as refined by Aquinas. The basic idea, though, is that every physical thing, living or not, has purpose or goal-directedness.
To use examples from Edward Feser, a more contemporary philosopher: the moon is directed toward movement around the earth; fire is directed to the production of heat; a heart has the purpose of pumping blood. Purposiveness implies change. Change means the movement from potential to actual, and that requires some actualizing agent to make the movement: heat to fuel causes a change in substance, e.g., from actual wood and potential fire, to actual fire, and so on. Every material thing is a combination of actual and potential, except one: the initial actualizing agent, which is itself pure actuality: God.
One of the four dimensions to physical reality screams this goal-directedness: time. Time actually does move and change. That’s why we perceive it as having a flow and a single direction. The universe (and time) started. It is now proceeding. It is going somewhere.
Enlightenment philosophers, such as Hume (18th century) and LaPlace (18th-19th century) and others posited a more determinist view, abandoning centuries of classical philosophy and embarking on what was, against all the evidence, a view that material reality just was—that there was no purposive element to it at all. The new atheists that have written in recent years, such as Sam Harris, Richard Dawkins, and Christopher Hitchens, purport to refute theism by taking the most helpful bits of this deterministic philosophy, and ignoring all the rest.
As Aristotle argued, and Plato in a different way, logic tells us that as soon as you recognize that there is a purpose to material reality, it inexorably points back to a creator who created with a purpose. There’s no escaping it.
Or to repeat an illustration Edward Feser used at the end of his book The Last Superstition, there is a saying attributed to Confucious, that when the finger points to the moon, the fool looks at the finger. Material reality is the finger, but it is pointing to something else. The fool sees only the finger, not understanding that the finger is a gesture to point us to the moon. So, as Feser says to the new atheists: “It’s the moon, stupid.”