I wrote some time ago a kind of letter-paper for my parents to communicate the reasons for my atheism. We have always had enough confidence to talk about everything, but as this is an "special" issue, I decided to talk to them and tell them my thoughts, but I found that a letter would complement the work. The arguments presented in the article, which divided into two parts, are only a part of all the arguments that I have about believing in God, but I think they are a good introduction to the topic. As can be noted at the outset, I use a phrase of St. Augustine, which I later used to write "St. Augustine's Misconceptions", which is the first article published on this blog. I hope you enjoy it.
I write this article mainly to tell you about something important as regards my ideology and my way of seeing the world. It could start by defining three concepts: theism, deism and atheism. The theism is the belief in a divine being (called God, Allah, Yahweh, Jehovah, Zeus, Thor, etc.) as creator and designer of our universe, a spiritual being omnipotent, omnipresent and omniscient, which intervenes directly and indirectly in the daily events of all people and also heard our prayers, read our minds and sometimes conceed some of our good wishes and / or desires.
The deism is conceptually similar to theism, with the difference that is given the name "God" to all processes and natural laws of our universe. The main difference between deism and theism is that a deist person doesn't believe in a God who listens prayers, nor acting directly and consciously in the world's events, but simply uses the label "God" to call the entire nature. Finally, atheism is the non belief in any kind of divinity. Generally, people who come to this point have done so after years of rational, objective and skeptical analysis of general natural phenomena. One thing you might notice is that an atheist have almost gone through each and every one of these three sequential phases as follows: theism - deism - atheism.
The concept of God is transmitted from generation to generation and usually we were instilled from an early age, becoming, after a short time, an inherent part of our way of thinking and seeing the world. In general, people never question religious issues, because there is a fear of divine punishment. As St. Augustine said:
"There is another form of temptation; even more fraught with danger. That is the disease of curiosity. It is it who prompts us to try to discover the secrets of nature; those secrets that are beyond our understanding, that not provide any advantage, and which man should not want to learn".
This is a sample of authoritarian and retrograde thinking of religion about human curiosity(tremendous blessing!, by the way). At this point it becomes necessary to take the next question: Why did not fit in any religion the deployment of high curiosity? The answer is very simple: Because religious doctrines are based on the blindfolded belief about several items (faith) and the most remarkable is that there's no evidence of anything that religion argue (and even, religion goes its way despite the evidence). If someone gets to think deeply and ask things about our existence and the many contradictions between the real world we see every day and religious doctrines and the concept of God, then many questionings regarding this situation will raise. Issues that often not arise because of an unconscious self-repression to think about profound existencial nature and natural issues.
So far I have not made much progress on this issue, but I think we already have been realized by where this letter is going. One thing that I must grasp is that my way of thinking today is not due to any disillusionment or disappointment or external influence. Far from it. For years I've been thinking so wobbly and intermittent in such matters, although in recent months in greater depth. The reasons that led me to not believe in God are purely rational, and I can say I am trying to maintain objectivity as far as possible. For a good time (several years) my way of thinking has been essentially Deist, but remained in me some characteristics of theistic thought. As I said earlier, the God concept is so ingrained in most humans that it is difficult to leave theism altogether.
There are many reasons that have led me to non-belief. In what follows, I will enumerate just some, because if I dwell too, I could write a book about it (it's really not a bad idea ...)
Before turning to my arguments, I think prudent to say that religion in which we grow is something relative to the birthplace. I was born in a country where Christianity dominates, so the influence to which I have been subjected (not only myself but all those born in these latitudes) has been clearly Christian. But now let's think a bit and let's supose that, instead of being born in Peru, I was born in Saudi Arabia, where I would be Muslim, or in Ancient Greece, where I would be worshipper of Zeus, or in today's India, where I would be polytheistic. But, does the absolute truth is found in only one of them? I think that every religion is built in different realities and according to very different cultural experiences among them. Now it seems to me appropriate to separate my reasons according to three different areas: sociology, philosophy and Epistemology ; Religion; and natural sciences.
Sociology, Philosophy and Epistemology:
In this part I will explain the humanistic ,philosophical and epistemological reasons that lead me to think about non-existence of any deity.
Feel protected: Human beings have the need to have some support or divine protection. Since ancient times, humans have been performed rituals and ceremonies honoring the gods in order to obtain the grace of these through rewards of nature: rain, favorable climates, fertile soils, etc. For hundreds of thousands of years, has taken root in our minds a need to be protected by some divine entity, whether God, Sun, Moon, Mother Earth, and so on. Even the evolution and natural selection favored the development of this cultural characteristic. Our ancestors created thousands of years the idea of a God (or gods) and they spread and transmitted it to the present day, using local legends and myths, or even metaphors and folk tales for that purpose. So now, perhaps for many people is something hard to think in a godless world.
The will of God: Religions taught us since historical times that our destiny is already said, and therefore, what often happens is God's will. Now, after this point several problems arise. The first I'll explain with an example: A person has a very sick parent and prays every day for his health. That parent is subjected to medical interventions and treatments to restore his health, but after some time, died. Now, a believer would say: It was God's will. But if we put ourselves in a case where an alternative parent is recovered and healthy, then the same believer would say: It was God's will .... Is not it absurd that reasoning? I think yes. Another problem for the will of God, is that if indeed things happen in their will, there would be a paradox (inconsistency) between His will and free will that supposedly gives us. Lets explain that as follows: The will of God is: death of a person's parent so that he temple or strengthen his character and could learn things, but at the same time, if he has to decide something in his life, whether good or bad, God leave him do his free will, ie not involved at all, hence, would not be God's will, but the person's will (that means free will, is'nt it?). This is clearly evidence that life situations occur by probability or estochastic circumstances and personal decisions, not by divine intervention (or not intervention). Furthermore, if God exists, would not be implemented perhaps the famous lex talionis  with all of us? If we do bad things, punishes us; if we do good things, we are rewarded. Personally, I seem all this absurd coming from a God almighty and omniscient.
Prayer: Most humans are accustomed to perform regular prayers in which they talk with God and they thank him and ask various things regarding us or our loved ones. If God answered our prayers as many argue and ensure very convinced, then we would expect to see a statistical trend towards the effectiveness of prayer. But such evidence does not exist at all. While it is true, many times we ask is met, which lies just to statistics runs issues (A statistical run is defined as a sequence of identical occurrences preceded and followed by different occurrences or none at all. To visualize and understand best this, this is an example: A coin has a face (F) and a stamp (S); Now, suppose we launched the currency several times. A likely outcome could be: F - SS - FFFF - SSS - FF - S -- F - SS - F. In this sequence could be seen 17 coin throwings, which results in 9 faces, 8 stamps and 9 runs. There is a statistical test to determine if the runs are due to chance or if some external factor intervened. In fact, there have been inquiries about this alleged phenomenon, but the results have been negative for prayer. On the other hand, if theists had positive results, would it not be conclusive evidence to affirm the existence of God?, However , despite many believer scientists have been behind these studies, the tests have failed).
If we have asked anything to God and then things happens as we ask, we tend to automatically say taht it was the work of God. However, we do not take into account real and simpler explanations such as statistics and probabilities, which explain natural phenomena accurately and satisfactory. But it must be admitted, that in many cases, the act of praying serves as a therapy for self-suggestion, which gives results only in psychosomatic illness cases.
Divine tests: Many times we say that things happen because God tests us. At first impression sounds logical, but if you delve further into the matter, it makes no sense whatsoever. Let me explain: What need is to God, an omniscient and omnipotent entity, prove the behaviour or reactions of inferior beings in relation to him if, as omniscient and omnipotent entity, he would know in advance what will happen or what we are going to decide? There is simply no response, because such situation does not make sense. On the other hand, as an omniscient and omnipotent entity, why would he might change his mind on something? (see remorse for having created the men and then kill all humans in the Universal Flood mentioned in Genesis, and many other examples in the Bible).
Play Dice?: In light of these considerations, I could analyze it a little more as follows: Assuming as real the existence of God, then we accept that he tests us every day and allows the life on Earth and its development in many ways; if this is true, then it would mean that God plays dice with us?, what does he would need to test our reactions or see them if he supposedly already know them since ever? The only reasonable answer I can make after the foregoing is that we are an experiment, a kind of pastime for God (if we assume that he's there).
Gaps: A thing that human beings do now and did in the past since ancient times is to fill the gaps in our knowledge with the idea of a god or several gods. The religion in general use these loopholes to explain mysteries (so nothing objectively) the existence and influence of any deity in our natural and social world. The science, antagonisticly, examines the nature as objectively as possible and use these mysteries to deepen our knowledge and research in them, to convert a mystery in a known process and explainable by natural laws. While religions require the existence of unchanged mysteries to explain their doctrines, science uses the same mysteries to study and analyze them and take away from them the label of mystery. In other words, the religious doctrines are based on ignorance of the nature and its mechanisms , while science allows us to get out of that ignorance and try to better understand our natural world. Over the course of human history, many mysteries have been solved (formerly regarded as unexplained things and issues attributed to divine), which has served to broaden the human beings's knowledge of nature. Personalities as Galileo Galilei, Copernicus, Darwin, Newton, Mendel, among others, were considered in his time as heretics by their contrary ideas to those imposed by religion. Ideas, which, now seems to be clearly consistent with the laws that govern this universe. Not even the scientific method is perfect, nor intended to give absolute truths, but is a very effective tool in analyzing a phenomenon, verify his correspondence with nature and draw conclusions from the most objective possible manner. And that is not all, but again and again theories can be reviewed and make corrections or discard them if necessary. At the other hand, the religion has many dogmas and doctrines and aims to remain unchanged and immune to any skeptical scrutiny, which preserves only ignorance and impedes the advancement of human knowledge.
 The epistemology designates the area of philosophical reflection that seeks to answer the question: How can we know if knowledge is true ...?
 lex talionis: An eye for an eye, a tooth for a tooth.