Observation suggests that the Universe has been designed
Intuitively, if we see a complex object which behaves in a coordinated way or which appears to have a purpose, we are likely to believe it was intentionally made by some agent. Experience almost always confirms this intuition.
For instance, a clock. Even to an alien with no knowledge of how we keep time, such a device would appear “artificial”.
Why else would it be there given that the number of arrangements of components which would all work together like that, is vanishingly small compared with what is possible.
Think of a structure such as Stonehenge. Nobody is sure what its purpose was but few would deny that it was intentionally made rather than being a random configuration of stones.
How much more for something as complex as a living creature which interacts well with its environment and how much more still for a conscious human being. And how much more again for a Universe which is fine tuned for the existence of life. In any other context, if we found an object like this, we would expect it to be an intentionally made artefact not just the result of impersonal natural forces.
The existence of a Creator follows naturally from what we see. A belief that the Universe in all its order and complexity “just is” requires justification even though there are those who, for whatever reason, consider it as self-evident.
The fine tuning of physical constants
Physicists have found that if the physical constants of the Universe were different from what they actually are by even a minuscule amount, then the Universe would never have formed and there would be no way for life to have appeared.
These constants include the strength of gravitational attraction, the strength of electrostatic attraction as well as many others.
The accuracy to which these constants must be set is mind blowing. Trying to hit a bullseye on an archery target on Mars by pointing a laser beam at it from Earth would be easy in comparison.
If any of these constants were varied by this kind of small amount then the Universe would either have collapsed back into itself after the Big Bang or would have expanded so rapidly that stars could not have formed.
The implication is that these constants were intentionally designed.
There are other possibilities, such as there being an infinity of other Universes, one of which just had to have the Goldilocks constants, but on the surface these seems much less probable and certainly no more probable.