In materialistic terms, human beings can be described as carbon-based biological life-forms with five highly specified sensor systems on board. Our highly developed meat computers, a.k.a. the human brain, manage these five sensor systems (sight, hearing, touch, smell, and taste) which allow us to perceive the cosmos around us while we think, will, emote, and act. This is what we are from the perspective of scientific naturalism. However, this description is still grossly lacking in explaining the human experience.
While the human biological machine is truly amazing, it is incredibly limited and finite. We exist on the razor's edge of a tiny piece of rock hurling around a small star out in the corner of a single galaxy in a very fine-tuned universe. If gravity was much greater (or less), or if the temperature range on the surface of the planet was more drastic due to even relatively small changes in the atmosphere, or if any similar small changes in the dozens of factors in the fine-tuning of the universe were different, we could not exist at all. The fact that we do exist seems incredibly improbable if this universe is all there is, and as far as we know from a materialist perspective this universe is all there is.
And that is the rub: As far as we know. We simply don't know a whole lot, at least not until very recently. Our built-in sensor systems are simply not that robust. Just take human sight, for example. The human eye can only see light between the wavelengths of 390 and 700 nanometers. We call this the "visible spectrum" because it is the only portion of the electromagnetic spectrum that a human eye can detect. Humanity didn't even know about non-visible electromagnetic radiation until 1800 when William Herschel discovered infrared light, so it is only in the last two hundred or so years that we were even aware of things like gamma rays, x-rays, ultra-violet light, microwaves, and radio waves. Before Herschel, all that stuff was beyond our perception.
This article would be too long if I got into the discovery of quantum mechanics, general and special relativity, and the DNA double-helix which are extremely recent discoveries, all pretty much in the last one hundred or so years. These four discoveries alone totally and radically changed our understanding of matter, space, time, and biological life. If you consider the last 100 years in the overall course of recorded human history of roughly 5,000 years, it has only been in this most recent 2% of recorded history that we learned about all this stuff. (If you believe the Darwinists, this is in the most recent 0.05% of human history since Darwinism might argue humans have been around for 200,000 years, but I digress.) Bottom line is for all but the most recent few years of human existence most of what we know today about physical reality was beyond our perception.
So, if all this stuff has been beyond our perception, what makes an atheist so sure that there is no God (or gods) out there beyond their perception? How can someone be so sure that God does not exist when for 98%, or 99.95% for the Darwinists, of human history we didn't know much of anything about the physical reality around us? What blows my mind is that otherwise intelligent people (a.k.a. atheists) disbelieve in the possibility of discovering God (or gods) when their supposedly scientific world view is based on discovery! The atheist mind does not welcome the possibility their human sensor systems have been unable to detect a God that transcends the natural realm. That level of inquiry is carefully carved out as off limits by an ad hoc assumption that the material realm is all there is of reality, and that (false) assumption is easily disproven. When it comes to the idea of God, the atheist mind snaps shut like a steel trap.
And that trap snap is just at the mention of the philosophical arguments for the existence of God. If you happen to venture into the topic that a philosophically possible God has been revealed in the best selling book of all time, pretty much every atheist will weave and dodge that evidence like a professional dodge ball player. That doesn't seem too "free thinking" to me. If you want evidence, dig in. Christianity is different from every other belief system. There is nearly 2,000 years of scholarship to examine, give or take a couple centuries for the dark ages where it was Christian monasteries that preserved knowledge. Take a look at the cartoon below to see how Christianity differs in simple terms from every other religion.
The unwavering faith the faithful disbelievers (a.k.a. atheists) have in Darwinism is stunning. The average Christian pales in their faithfulness as compared to the average atheist. According to perhaps the most famous atheist on the planet today, Richard Dawkins, "Although atheism might have been logically tenable before Darwin, Darwin made it possible to be an intellectually fulfilled atheist." [The Blind Watchmaker (1986), p. 6] If you discount atheists who have a predisposed penchant for the dogma of Darwinism, which includes a large portion of the scientific community which is disproportionately atheist, pretty much every other thinking person on the planet understands what Intelligent Design looks like. If you see a wrist watch laying on the beach, you don't think all those parts just randomly came together out of the primordial ooze of the ocean by chance over billions of years. You know there was an intelligent watchmaker involved in designing and making the watch. Even a five year old understands this without any formal schooling.
You have to be a highly trained scientist like Richard Dawkins to unlearn this human intuition, plus you have to go to extraordinary lengths to explain away reason with the pixie dust of "billions of years" and fairy tales about amoebas evolving into higher life forms which eventually evolve into the lower primates and then finally homo sapiens. It goes against all rationality considering the complex design of the inner workings of a single cell, much less the highly developed carbon-based biological life-forms with five highly specified sensor systems on board. But, I guess if you need a reason to not believe in God, any silly reason will do. Never mind the possibility that perhaps God is just beyond the perception of the atheist like pretty much all of modern scientific understanding for 99.95% of human history, to use the Darwinists' numbers.