Can't you tell?

"For since the creation of the world God's invisible qualities--his eternal power and divine nature--have been clearly seen, being understood from what has been made, so that people are without excuse." Romans 1.20

While the "argument from design" appeals to the intricate nature of specific objects as evidence of an intelligent source, the "teleological argument" considers whether the whole nature of existence is best understood as having been carefully and deliberately crafted. British philosopher FR Tennant offered 5 factors in support of his thesis that the scope and integrity of the natural order is best understood as the product of a theistic Being (ie God!).

First is the harmony between the way we think and how life actually works. Then there is the progressive nature of evolution which is suggestive of purpose and direction. Thirdly, the suitability of the natural order as a "theatre of creation", as in the way Genesis begins by describing the realms of space, sea and land before populating them with stars, birds and fish, animals and people. Fourthly is the aesthetic appeal of much of the created order, which resonates with our own appreciation of beauty and order; where did that come from? And, finally, the instinctive moral awareness to which our consciences bear witness, suggesting that we are accountable to more than ourselves...

Of course none of these factors are prove-able in a scientific way. As factors affirming the existence of God their appeal lies in whether one considers them convincing or not and that will depend on whether our minds are open to persuasion, or already made up.