Atheism is, in the broadest sense, the absence of belief in the existence of deities. Less broadly, atheism is the rejection of belief that any deities exist. In an even narrower sense, atheism is specifically the position that there are no deities. Atheism is contrasted with theism, which, in its most general form, is the belief that at least one deity exists.
In defense of St. Thomas Aquinas' five ways. A response to the philosopher Fernando Savater
By Dante Urbina
St. Thomas Aquinas' five ways are definitely a key milestone in the history of philosophy. Their purpose is to rationally demonstrate God's existence. How? Well, starting from the wise advice from Aristotle about that, regardless of how we will perform a demonstration, “what is certain is that we must start from what is known”.Thus, St. Thomas starts with certain well-established features of the world we know such as movement, causality, contingency, degrees of perfection and order; then, through a rigorous logical process, he arrives at the existence of a Prime mover, an Uncaused cause, a Subsistent being, a Pure perfection and an Intelligent mind, respectively, all of which corresponds, of course, with concept of God in an univocal way.
Well, St. Thomas Aquinas lived in the thirteenth century and therefore had no opportunity to respond to criticism that will be subsequently performed by philosophers and thinkers such as David Hume, Immanuel Kant, Arthur Schopenhauer, Bertrand Russell, Graham Oppy, etc. However, in my book (currently available in Spanish) Does God exist?: The book that every believer will must (and every atheist will fear) read I give a direct response to all these criticisms and much more, showing the tremendous depth and strength of St. Thomas Aquinas' five ways when they are understood in their proper philosophical context and illustrated with the latest scientific advances.
So, as an example of this, I will respond to a critique of the five ways performed by one of the most famous and influential philosophers of our times: Fernando Savater. In one of his speeches in the TV program about philosophy “The Adventure of Thought” he says regarding the Thomist ways: “Obviously, history has not accepted a large part of the five ways which are due to an ancient physics and a very dubious knowledge about the world, and especially to a misunderstanding that is that you cannot explain what we do not know by mean of something we know even less. That is, we know little about the origin of the universe but nothing about God. So, from saying that God explains the origin of the universe follows an immediate question: And who explain God? This would be the end of the matter, but obviously neither St. Thomasnor his time allowed go so far”.
In what follows, the point-by-point rebuttal to what was said by Savater (I quote his words and then introduce my comments):
1) “Obviously, history has not accepted a large part of the five ways…”: Obviously Savater's opinion in this regard is based on either an exaggeration or a very dubious knowledge about history. There is no such thing as “History has not accepted a large part of the five ways”, strictly speaking what has existed is a group of thinkers at certain times in history (especially from the eighteenth century) who have rejected the five ways. But it has not constituted an unanimous or permanent position at all. Even more, nowadays the debate on the five ways, rather than being a finished issue, it is an issue that has returned in a very strong way to intellectual and academic fields in various forms. If in the late nineteenth century we found that “philosophy”, along with Nietzsche, proclaimed “God is dead!”, now, in the early twenty-first century, we clearly find that “He is risen!” in the sense of that theism returns to be the subject of serious debate even in the most renowned universities in the world. If Mr. Savater does not know this and just wants “to look away” regarding this reality, it is another problem...
2) “… which are due to an ancient physics and a very dubious knowledge about the world”: In this, it seems that Savater has “a very dubious knowledge” of the Thomistic philosophy. It is true that St. Thomas Aquinas appeals to the (limited) scientific knowledge of his time in order to illustrate his arguments, but these are eminently philosophical arguments and therefore their validity is much more general and transcendent and does not depend on this or that situation in the advance of scientific knowledge. To prove this, let's look at the most common case which is mentioned in this type of criticism. Regarding the first way, which starts from the existence of the movement to deduce that, given that there cannot be an infinite chain of movement,there must be a First being which cannot be moved by another and instead gives the principle of movement to all the rest, we found that the common critique is: “That way is invalid because Thomas Aquinas' understanding on the movement was based on Aristotle's physics, which was obviously very flawed and has become outdated”. And yes, the Aristotle's physics was too basic. But it turns out that the philosophical background of the first Thomist way is not this or that Aristotle's old scientific theory but rather the most fundamental and general philosophical concept that he gave about movement. Thus, in Aristotelian philosophy, movement is defined as “the act of what is in potency in terms of potency”. That is, the movement is the passage from potency to act. Is this compatible only with the old vision of the movement in terms of simple mechanical locomotion? Not at all, the passage from potency to act is something quite general and can be compatible with more sophisticated scientific views on the movement that can incorporate issues such as inertia, quantum physics, relativity theory, chaos theory, etc.
3) “… and a very dubious knowledge about the world, and especially to a misunderstanding that is that you cannot explain what we do not know by mean of something we know even less. That is, we know little about the origin of the universe but nothing about God”: It is really surprising that a skeptical philosopher can say such a thing (in the first sentence) as that we know “even less” about the universe than what we know about God. And this because, outside the realm of faith, for human beings in general what is material (body, universe) is much better known that what is immaterial (soul, God). Therefore, the Aristotelian-Thomistic method is still perfectly appropriate to prove the existence of God: starting from what is known arrive to what is unknown. Additionally, it is not true that the universe is absolutely unknown to us. We have a limited knowledge about the universe, of course, but much of that knowledge is well established. May be we do not have full all the “crossword puzzle” of the universe, but we have made progress to fill several parts and we can trust in it (not as a dogma, but rather as a valid knowledge). As astrophysicist Paul Davies says: “I often liken fundamental science to doing crossword puzzle. (...) With each new solution, we glimpse a bit more of the overall pattern of nature. As in a crossword, so with the physical universe, we find that the solutions to independent clues link together in a consistent and supportive way to form a coherent unity, so that, the more clues we solve, the easier we find it to fill in the missing features”. What advances in our knowledge of the universe and its origins we have had in recent decades? Well, let's see: Big Bang theory which, as standard model, establishes an absolute beginning of the universe from literally nothing; Penrose-Hawking singularity theorem which demonstrates that with the beginning of the universe begins to exist not only matter but also space and time themselves; Borde-Guth-Vilenkin theorem which generalizes the above independently of the “Planck time” and even possible scenarios of expanding multiverses; and fine tuning, which states that arbitrary initial conditions of the universe have to be extremely special for the emergence of intelligent and interactive life like ours. Does all this point to an immaterial, timeless, spaceless and intelligent First cause behind the universe? It seems so and all this is explained in detail in my book Does God exist? So, contrary to what Savater wants to imply, I have to say what I defended in a public discussion with an atheist physicist and an agnostic philosopher: physics does point to the existence of God. And this, of course, consistently with Thomas Aquinas' philosophical approaches.
4) “So, from saying that God explains the origin of the universe follows an immediate question: And who explain God? This would be the end of the matter, but obviously neither St. Thomas nor his time allowed go so far”: It can be expected that an atheist with low philosophical training, like Richard Dawkins, for example, can express such type of criticism. But it is quite striking to see that a renowned philosopher like Savater says “Who created God?”. In a scathing way, he says: “This would be the end of the matter, but obviously neither St. Thomas nor his time allowed go so far”. No, that is not the end of the matter, we can still take an additional step, namely: “Does it make sense to problematize the question itself?”. And turns out that the answer is yes. If, according to classical theism, God is defined as the “Subsistent being”, we will have that the question would be: “And who created the Subsistent being, i.e., the being that does not depend on other being for its existence”. Or, if we take the second way which reaches God as “Uncaused cause”, the question would be formulated as: “What caused the Uncaused cause, i.e., the cause that has no cause?”. It is clear that ask things like these is as absurd as asking about a “square circle”. One can understand that someone to say that there is no Uncaused cause, but what cannot be understood is that someone to say that you can propose as something coherent, though it be as a question, whether there is a “caused uncaused cause”. So, it is not that Aquinas' thought does not allow “go so far” but rather that Savater's biases and his lack of depth in this regard are those that do not allow him to go so far in order to put into question the question itself. This is typical of certain skeptical thinkers: they are very critical regarding theism and very dogmatic regarding their own criticism. It is also necessary to be skeptical about skepticism itself.NOTES
 Aristotle, Nicomachean Ethics, Bk. I, ch. 4.
 Dante A. Urbina, ¿Dios existe?: El libro que todo creyente deberá (y todo ateo temerá) leer, CreateSpace Press, Charleston, 2016.
 Fernando Savater, “Santo Tomás de Aquino”, in: La Aventura del Pensamiento (TV program), Encuentro channel, 2008, ch. 3.
 . Aristotle, Physics, Bk. III, ch. 1.
 Paul Davies, The Mind of God: The scientific basis for a rational world, Ed. Simon&Shuster, New York, 1992, ch. 5.
 Dante A. Urbina, Luis del Castillo and Humberto Quispe, “¿Apunta la física hacia la existencia de Dios?” (Dialogue), Universidad Nacional Mayor de San Marcos, Lima - Peru, December 4, 2015.