When discussing the existence of God, the theists often express the opinion that the existence of God is obvious. Just look around you, they say, look at the magnificent structure of the universe, the beauty of nature, and the fine tuning of the natural forces, fine tuned to make life possible. In fact, a small deviation from the values of the fundamental forces would make life impossible, therefore, there must be an intelligent designer. They express astonishment that non-theists do not see that a supernatural power must exist.
To the unbelievers, their observations of reality come to the opposite conclusion. They often express astonishment, when the facts are observed, that someone would think that God is perfect instead of incompetent, especially when we look closely at the life-forms around us.
Looking at nature, we find many flaws in plants and animals currently occupying the planet. We also know, through archaeology and paleontology, that over 90% of the species which have ever lived are extinct. Those species, in many cases, could not adapt to changes in the earth’s climate.
Humans are at the top of the food chain. Viruses and bacteria attack all life forms and many species still show vestiges from previous forms, such as in the human tailbone, indicating that only by changing and adaptation do species survive. We are still evolving. Evolution never stops and most random changes are not viable unless, by chance, they fit the changing environment.
Disasters and diseases are part of life. The universe is 99.9% hostile to life. Life on earth could be wiped out by chance if an errant large meteorite hit this small little vulnerable rock circling around the sun which will itself eventually destroy this tiny planet.
Theists often point to the complexity of the human eye. They assert that the human eye could not have evolved without an intelligent designer. However, when we look at all of the various forms and structures of eyes across a myriad of species, we find all sorts of structures from very simple light detecting patches to complicated insect eyes which evolved in totally different ways, exposing how the random processes of evolution work. Only useful adaptions, out of many, will survive for a while.
Another argument Theists like to mention is that the random electrical and chemical events needed to form the first self-replicating molecule are highly improbable and would need to overcome such enormous odds that the universe is not old enough for such events to happen. This indicates the misunderstanding of odds. We can observe that lotteries, with millions of odds, have winners every few weeks. You could win tomorrow! It doesn’t take millions of draws to produce a winner and certainly a universe with “zillions” of “draws” every femto-second could have more than one winner, although we are sure of only one winner, since we are here. Help from a divine entity is not required.
For all the above reasons and through observing nature, life is actually full of design imperfections which indicate random development rather than intelligent design. We won the lottery so make the best of it.