The Philosophical Search for God - Book Summary and Analysis of "God and Philosophy" by Etienne Gilson

Book Summary and Analysis - God and Philosophy by Etienne Gilson

Etienne Gilson, a famous Thomistic philosopher of the 20th century, wrote a work called God and Philosophy. The book is a history of the Western notion of God. He investigates the idea of God from the Ancient Greeks through today, confronting what the idea and “problem of God” is as well. He shows not just what people thought, but what ideas worked and what did not, as well as drawing the conclusion of the metaphysical necessity of God as the self-existing being-itself. This post summarizes his book chapter by chapter, and then considers how the root of the problem of so many philosophers of the modern age is their theory of knowledge. Gilson says that the intent of this book is to fully and truly set up the problem of God’s existence in its fullness, and then to answer the question himself giving it the necessary metaphysical depth (Gilson XV/XVI).

Chapter One - God and the Ancient Greeks

Gilson says that Western society comes in many ways from the Ancient Greeks. Even the natural idea of God was aided in its development by the Greeks, though in stages. Thales, an early Greek philosopher, held that everything came from water and will return to it. But he also is quoted as saying that “‘all things are full of gods.’” Gilson seeks to find what Thales really meant by saying these seemingly contradictory things (Gilson 1). Gilson says that while this is a difficult thing to figure out, people often make conclusions about these philosophers that are incorrect, and are not really what the philosophers meant (Gilson 3). One man proposed that Thales use of god was not religious at all, but that he was just referring to water’s natural power. Gilson says that there is not a more religiously meaning word than the word god (Gilson 4). Gilson suggests we just take him literally on what he says. To do this, one needs to understand the notion of the word god from that early Greek period (Gilson 5). The word god for them first came from theological poetry, and was already around when the philosophers came on the scene. For the poets, the word god could mean a person, a natural force, and other things that govern man’s life, such as death or sleep (Gilson 6/7). Gilson says that there is a common theme to the gods though:
“Whatever the real nature of what they designate, these names of gods all point to living powers, or forces, endowed with a will of their own, operating in human lives and swaying human destinies from above (Gilson 7/8).”
A religious Greek felt that he was subject to all these gods, and was in a sense controlled by them (Gilson 8). 

Gilson then identifies three characteristics of the gods. First, gods are always living things, like man. Second, gods are related to man somehow, they are things that affect his life (Gilson 9). Third, each god is usually the greatest of its dominion, but is subject to others gods with regard to other things. For example, Gilson says that all men and immortals are subject to the god of sleep (Gilson 10). Even Zeus, the father of all the gods, has to be subject to fate and destiny (Gilson 10/11). So Gilson says the definition of god should then be: “a god, to any living being, is any other living being whom he knows as lording it over his own life (Gilson 11/12).” All these living forces could affect a man’s life, so one must be respectful to the gods. They could make you strong and fierce, or they could shipwreck you (Gilson 12).

Returning to Thales... While it seems likely that Thales was moving away from the more Homeric idea of the gods, it still does not make sense to posit water as the one god that makes up everything, and also that "everything is full of gods" (Gilson 13). It seems that Thales was holding that water makes up everything and is the one ultimate god, but there are still the lesser gods. These lesser gods would not be the ultimate in their dominion anymore, but now water would be (Gilson 14). It would be hard, though, for people to give up their gods to accept this one unifying water theory, because water is just a thing (Gilson 16). The Greeks viewed the word very scientifically, asking what are things, and what are they made of (Gilson 16/17)? “Taking the world as a given reality, the Greek philosophers simply asked themselves what its “‘nature’” was, that is, what was the essential substance of all things and the hidden principle of all their operations (Gilson 17)?” So again, coming up with ideas like fire, or water (Gilson 17), there is that problem of reconciling the philosophical conclusions of the Greeks. Gilson says that there is the idea in both that everything happens by necessity. But there is a difficulty, in philosophy, necessity is just a law, but the necessity in religion of the fates it a free will (Gilson 19). Gilson says that a first principle from which everything comes, for the Greeks, was an idea. And that because man alone in creation is able to recognize that he is self-aware, there the first principle of everything must too have this characteristic or better (Gilson 20/21). Also, Gilson says that man sees himself as different from everything else, in that he alone is able to make free decisions. He has a free will (Gilson 21). Therefore, the first principle must at least have this as well.

This idea, that because man is self-conscious and is free therefore the powers of the universe must also be this, Gilson says this is the foundation for the Greek religion (Gilson 22). But he says that this is not the foundation for philosophy and that Greek philosophy is not just a rationalizing of their religion (Gilson 22/23). “…Greek philosophy was a rational attempt to understand the world as a world of things, whereas Greek mythology expressed the firm decision of man not to be left alone, the only person in a world of deaf and dumb things (Gilson 23).” So one can see it was first hard for them to reconcile this idea that all was all water or some other inanimate substance, and the idea of god from their religion (Gilson 23). 

When Plato comes along, he holds the idea that the most real things are those that are necessary, as well as intelligible (Gilson 23). Because material things are always changing, they are not necessary or intelligible (Gilson 23/24). Therefore, for Plato the most real things are the intelligible forms of these things.

“Truly to be means to be immaterial, immutable, necessary, and intelligible. That is precisely what Plato calls Idea (Gilson 24).”
The being of things comes from their sharing in the eternal essence of the thing (Gilson 24). Plato puts, even higher than those forms, the form of the good because all other things participate in the form of goodness (Gilson 25). But Gilson says that Plato never considered these things gods. They are just ideas (Gilson 26). For Plato, the gods were lesser than the ideas and forms. A god for Plato is like the sun, it is a living singular being (Gilson 27), but “intelligible, immutable, necessary, and eternal (Gilson 28).” They share many of the qualities of ideas, but are still lesser. Human souls, to Plato are all gods. Also after Plato takes some of the imperfections from some of the traditional gods, he includes them too, so there are a whole bunch of gods (Gilson 28). So in the end Plato keeps both the philosophical principle and the gods as well. To be religious for him is to honor the traditional gods. And a philosopher for Plato is just someone who remembers that he is a god and acts like it (Gilson 29). Plato says that everything that is living and moves itself must have a soul, and therefore be a god too (Gilson 31). 

Next comes Aristotle. He says that the origin of our idea philosophical idea of god comes from men’s souls and the motion of the stars. He made the long awaited leap to considering the first principle to include the idea of the supreme god. “The prime mover of the Aristotelian universe is also its supreme god (Gilson 32).” This basically eliminated the former Greek gods (Gilson 32). For Aristotle, the supreme god is “…not an Idea but a self-subsisting and eternal Act of thinking. Let us call it Thought: a divine self-thinking Thought (Gilson 33).” This divine thought does not create the world, the world always existed. The divine thought thinks only of himself (Gilson 33), he does not know anything “as distinct from himself (Gilson 34).” Below that are lesser and moved gods, the “concentric heavenly spheres (Gilson 33),” which cause the movement of the universe. But does Aristotle’s philosophy do away with their religion, Gilson asks (Gilson 33). Since god is aloof from man, the highest goal is to contemplate him. But only a very few reach this, and only for a very short time. Then, therefore, people should seek to have practical wisdom. It does seem that Aristotle did away with the former religious gods (Gilson 34).

Chapter Two

While the Greeks were unsure about how to reconcile their gods with their philosophy, and the first principle of all things, the Jews on the other hand without a philosophy received great insight from the true God himself. He told them directly that he is only one (Gilson 38). Therefore, anyone who knew philosophy and knew the Jewish God, would see that the first principle and God are one. The Jews knew God to be someone, a father, taking care of them (Gilson 39). The Jew’s asked God what his name was. God told Moses that his name is “I AM WHO AM (Gilson 40).” This, Gilson says, is like a short-cut for the Jews because they did not discover this in their deep thought of metaphysics, but just asked God directly (Gilson 40). With the spreading of the Gospel, those Greeks who knew philosophy would again see that the first principle was the same as “I AM WHO AM.” By this time, the old Greek gods had been long left behind (Gilson 41). Plato’s philosophy is one which looks very similar to what the Christians were saying, but the first principle for Christians is a someone, not just a something (Gilson 42). The idea that the supreme cause is a someone that exists, of whom is not known his direct essence, just his existence (Gilson 43/44). This causes a shift to be more focused on studying the fundamental aspects of reality, that of existence and being, than the Greeks just looking at the nature of things in nature (Gilson 44). 

Augustine, having read Plotinus, tries to use his ideas to explain the Trinity (Gilson 48). But Gilson says that the two philosophies are incompatible because the One in Plotinus is completely "other" than the being of everything else, yet it is supposed to be the principle from which all else comes. It is contradictory (Gilson 50/51). In the metaphysics of the Christians, since God is “He Who Is,” He includes all existence in Himself in a perfect totality (Gilson 51). Therefore, it is not possible for there to be two Gods, yet one sees that there are other beings than this God (Gilson 52). These beings must not be gods, like in the idea of the pagans, but must be a lesser creation by God (Gilson 53). God is the only divine One now, and there is an infinite gap between the perfectness of the being of God and the finite being of man (Gilson 53/54). Augustine, again, tried to use the philosophy of Plotinus to explain the Christian God (Gilson 54). He says that the supreme intellect in Plotinus is equal to John the Apostle’s writing of Jesus as the Eternal Word of God, through which one is brought to the knowledge of God. But Augustine had to deal with the problems of using their philosophy (Gilson 55). Plato and Plotinus believed that the soul was a god, and that one is trapped in the body at birth, forgetting that they are a god (Gilson 55/56). It is man’s knowledge of the immaterial and immortal that makes him divine (Gilson 57). Augustine had to reconcile this with Christianity, which holds that naturally man is not a god (Gilson 58). So Augustine, holding that knowledge is still divine, says that God must give man the light of knowledge to know in this way, or he would not have the knowledge. Thus, he sees man’s knowledge as a sort of proof for God’s existence (Gilson 59). Augustine, though, because he uses the philosophy of Plato and Plotinus does not quite reach the correct idea that existence must accompany every essence. The most real beings to them, ideas, are essences, and existence is not correctly considered (Gilson 61). This left those Greeks, and Augustine, with problems.

It was not until St. Thomas Aquinas discovered Aristotle in the 1200’s that there was a breakthrough with philosophy and Christianity. Aquinas takes Aristotle’s insights and revamps them with the truths of Christianity (Gilson 62). Aquinas comes to a metaphysical breakthrough (Gilson 67). While Aristotle saw the first principle as not just a thing, but as the supreme god (thought thinking itselfhe still was lacking, like the other Greeks, in the idea that existence underlies everything (Gilson 66). “This infinitely powerful actuality of a self-thinking principle most certainly deserves to be called a pure Act, but it was a pure Act in the order of knowing, not in that of existence (Gilson 66).” Thomas sees this, and thus God is now seen philosophically as pure existence (Gilson 66/67). Everything, therefore, has a dependence in being on God for its existence (Gilson 65). Thomas develops the idea of "esse", or "actus essendi," (to be or the act of being) which is the fundamental act of existence which everything that exists has in some manner to make it the thing that it is (Gilson 69/70). This truth is a hard one to see because this fundamental act is not experienced directly by man, but only indirectly. In the universe one only experiences certain essences, certain things, never anything that is just pure existence (Gilson 70). Since no empirical thing is existence itself, then the thing can be thought of as not existing, and it rightly does cease to exist (Gilson 71). (Even the existence of fundamental matter cannot exist by itself, because it cannot move or create itself, and it is shown that it is moved and created). The limited being of all the material universe points to God as its cause, the one being whose definition of His nature is “to be” (Gilson 71/72). Essence and existence are the same in God. One then can see God in all of creation because all of creation depends on Him for its existence (Gilson 72).
“‘all knowing beings implicitly know God in any and every thing that they know (Gilson 73).’”
These were the highest of truths that Aquinas reached, unfortunately, they were soon lost after this period (Gilson 73). 

Chapter Three

Chapter three first deals with Descartes. The Renaissance was a time which moved away from the Church doing philosophy, and took a very secular turn (Gilson 74). Descartes, although a Catholic, wanted to separate faith and reason (Gilson 75). He wanted to do a philosophy that was completely natural. “As a philosopher, however, Descartes was after an entirely different sort of wisdom, that is, the rational knowledge ‘of the first causes and of the true principles whence the reasons of all that which it is possible to know can be deduced.'' Such is the natural and human good, ‘considered by natural reason without the light of faith (Gilson 77).’” He holds that this idea of God as “… a thinking, uncreated, and independent substance… (Gilson 81),” and it is innate in every man (Gilson 81). And because man’s innate idea of God is a being whose essence must exist as existence is part of it, then God must exist, otherwise it is a contradiction (Gilson 81/82). Descartes takes the Christian God and reduces him to a “first philosophical principle (Gilson 85),” that is, he loses the notion from Thomas of God as total perfection of being in Himself, and reduces Him again to the Greek notion of just a first principle for everything else. The Cartesian world was mechanistic and mathematical (Gilson 86). So God, as first cause, was reduced to his function (Gilson 87). “… the God of St. Thomas was an infinite ocean of existence, the God of Descartes is an infinitely powerful fountain of existence (Gilson 87).” God’s essence now is not just to be, but it is to create (Gilson 88). This has serious consequences on who God is because it reduces God to “The Author of Nature (Gilson 89).” This, Gilson says, is just as bad as making nature a god (Gilson 89). And many of Descartes later followers will do just this (Gilson 90). Descartes' main goal was to break away from religion and philosophy being together, and to accomplish a complete natural theology. Thomas deepens Aristotle to develop his Metaphysics through the guidance of Christianity, Descartes wants to develop his philosophy without any guidance from religion whatsoever (Gilson 90).

One of the people who took Descartes' philosophy to its natural conclusion was Spinoza. For Spinoza, the existence of something follows from the nature of the thing. Therefore, the only being that could be thought of who has existence by necessity is God (Gilson 100/101). Therefore, God alone exists but just as a nature, not as a person, Logically it would follow that God would be nature, or everything that one sees existing (Gilson 101). This is pantheism. His problem is that he starts from a logical position conceiving that the existence of everything comes from its nature, and one needs to move back to looking at what exists, and then seeing its nature from its existence (Gilson 103). 

Then next position Gilson talks about is Deism. They rejected revealed religion and said that their God could be naturally known (Gilson 104). But Gilson points out that their notion of God was different from other philosophers (Gilson 104/5). It was more of just a left over watered down idea of the Christian God (Gilson 106). Having rejected Christianity, and not understanding philosophically the correct notion of God (maybe following Descartes and his natural theology), they were reduced to holding onto God as a far off principle to at least posit the creation of the world and all its laws. But God turned into more of a myth (Gilson 107), which the generations after them came to reject (Gilson 108).

Chapter Four

Gilson says that the modern day problem of God is very well seen in the two philosophers: Immanuel Kant and Auguste Comte. They both reduce all knowledge to scientific or empirical knowledge, and so to know is for there to be a relation between things on a mathematical or empirical level. This has big consequences though, because since one does not experience God empirically, then no real knowledge about God exists (Gilson 109). Gilson says that the Christians built upon the Greeks, and the new Renaissance used the Scholastic's language to say new things, but the Moderns are a total break (Gilson 110/111). They say that since God is not experienced in the senses, there is no reason to hold Him as real, but just as a composition, or a unification, of ideas that one puts together in the mind (Gilson 111). Comte rejects the idea of causality, but this cuts out any room for why questions, which cuts out any room for seeking God (Gilson 112). “To dismiss all such questions (why) as irrelevant to the order of positive knowledge is, at the same time, to cut the very root of all speculation concerning the nature and existence of God (Gilson 112).”

All the Moderns want to reduce knowledge and explanations simply to science; to have it be completely finalized and done, no more explanations needed (Gilson 113). “Whatever their many differences, all these schools have at least this in common, that their ambition does not extend beyond achieving a rational interpretation of the world of science given as an irreducible and ultimate fact (Gilson 113).” Gilson says that today one sees that from after Aquinas to Kant everything was used, whether they were conscious of it or not, as a ghost of the Christian God. They, therefore, were just bad spinoffs of Aquinas. So man today is faced with either choosing the actual Aquinas or with Kant and other Moderns. Unfortunately, he says, that many choose to go with Kant because the truths of science/math are so clear and precise (Gilson 114). Likewise, by accepting this total empiricism they claim to do away with God.

Gilson replies to this that even aside from philosophical proofs for God, there is a natural spontaneous knowledge or wondering about God that arises in each person (Gilson 115). Kind of like how the Greeks had that natural sense that there must be gods. When one sees the greatness of the world, or of one’s solitude or of one’s death, the human person naturally goes to that question of God. Gilson is not saying that these are proofs, but simply facts of life (Gilson 116). He says that even Kant and Pascal, while not holding onto God by reason, held onto God. There was something there that must have compelled them (Gilson 117). Everyone naturally is faced with at least the question and thought of God.

Whether we make it the result of spontaneous judgment of reason, with Thomas Aquinas; or an innate idea, with Descartes; or an intellectual intuition, with Malebranche; or an idea born of the unifying power of human reason, with Kant; or a phantasm of human imagination, with Thomas Henry Huxley, this common notion of God is there as a practically universal fact whose speculative value may well be disputed, but whose existence cannot be denied (Gilson 118).

But Gilson says, then the idea must be tested to see if it is really existing. Well, it is obvious that God is not directly able to be experienced by the senses, therefore empirically testing for God is not the right method (Gilson 118/119). The way to test this idea is by reason, but in the order of abstract truth, philosophy, as a metaphysical question. Science is for finding out what something is, but it does not show why things are. The answer for these questions of why, are not empirical. The notion of God is a why question (Gilson 119). This question can only be dealt with by metaphysics, the study of being as such (Gilson 120).

It is true the universe seems to be a mysterious place, and science works to lessen this, but they often try to answer the why questions with science ... but they cannot do it, and so the universe does seem mysterious (Gilson 123). Science often tries to give ridiculous explanations for the why questions (Gilson 124). To ask why something happened, or exists, is to seek after the thing's causes (Gilson 126). Why is there order in the universe? Scientists say that it is just chance. But when the universe is so perfectly ordered, this Gilson says, seems to be a weak answer. So other scientists say that “mechanical laws” did it; but these are the opposite of chance. Then, when the question comes to the origin of life, they go back to chance (Gilson 127). Science’s answers often fall into non-sense when trying to answer why. Why, Gilson asks, do they then so forcefully impose their views on everyone? Well, because, “They prefer to say anything rather than to ascribe existence to God on the ground that a purpose exists in the universe (Gilson 128).”

It is clear to all, Gilson says, that living things appear to have an order to them. He says that if science could, it would explain the origin of life by its mechanical laws, but it cannot (Gilson 129). When they do not see scientific intelligibility in their observations, they would rather hold crazy claims and theories, to try and make it work, than to possibly admit to a “nonscientific intelligibility (Gilson 130).” For an example of this see page 130. A non-empirical purpose or cause to something is of a different nature than all their empirical causes (Gilson 131). Science cannot explain final causes, and often without metaphysics, reduces their world to a world of just appearances. But metaphysics does have answers to these other types of questions and reasons (Gilson 132). It can show us the purpose of something, of design. And since design and purpose come only from a thinking thing, then an intelligent being must have been behind it. Huxley says that purpose in nature is man’s projection of purpose where there really is none. Gilson says, yes, maybe man may project purpose, but man is a part of nature, and man for sure acts for a purpose. Therefore, there is purpose in nature (Gilson 133/134). Some reject this as “a common fallacy (Gilson 134).” Huxley says that purpose is really just a natural adaptation, and that there is nothing special about it (Gilson 134/135). Gilson does not accept this, and says: “It is the fallacy of a scientist who, because he does not know how to ask metaphysical problems, obstinately refuses their correct metaphysical answers (Gilson 135).”

A world that does not recognize the metaphysical realm, and God, is back again to Thales, and to many pagan gods. In society today, man has let these errors rule (Gilson 136). It is only in coming back to metaphysically correct thinking that man will have a good society. “Much more common, unfortunately, are those pseudo-agnostics who, because they combine scientific knowledge and social generosity with a complete lack of philosophical culture, substitute dangerous mythologies for the natural theology which they do not even understand (Gilson 137).” The question of purpose and order to things is a question that occupies Moderns a lot today, but why things exist is a question that is even deeper (Gilson 138.) Empirical science cannot even ask this question, Gilson says. Gilson says that the only answer to this question on the level of reason is that everything that exists owes its existence to something that is pure existence and exists in itself (Gilson 139). This being also then freely creates, for the being exists perfectly in and by itself as absolute and self-sufficient being. Since one sees that its creation has order to it, and the only way man has ever found order has been from thought, then this being must have thought, and is a person (Gilson 140).But this is not to make the claim that the essence of God is known directly, but only indirectly through His effects. One knows the proposition God exists, again, not by direct experience, but by showing this as a necessity from the effects of being (Gilson 142/143). “The ultimate effort of true metaphysics is to posit an Act by an act, that is, to posit by an act of judging the supreme Act of existing whose very essence, because it is to be, passes human understanding (Gilson 143).” Man must seek the “mystery of existence (Gilson 143).” Gilson ends by saying that the man who can keep the whole of truth will be the one to recognize that the “He Who is” of philosophy is the same as the “HE WHO IS” of Judaism and Christianity (Gilson 144). 


It seems to be common in all the philosophers mentioned after Aquinas by Gilson that the reason they departed from the truth was because they had something wrong with their theory of knowledge, with how they knew. Descartes did this in doubting his senses. Kant did this with his whole system of knowledge, saying that the senses only give one scrambled, unintelligible, information which our a priori concepts then order to give one knowledge. But Kant’s knowledge is not of the real world, he never is able to get back to knowing real things. The Positivist and scientists, which Gilson talked about, did this by rejecting any truth but that which is empirically or mathematically proved. In many cases, people go wrong with their theory of knowledge because they require strict demonstration to prove that they know things. Descartes wanted to build his whole system on this. He wanted to create a strict demonstration as the basis for all knowledge. Also, this is what Kant and the Positivists are doing when they only accept empirical knowledge. Certain types of knowledge can be strictly demonstrated, but if that is the only truth that can be known, then there are big problems. This is because if strict demonstration was required for everything, there would be an infinite regress in knowledge, and nothing could ever be known. This is because there would always be the need to prove one truth with another scientific or mathematical demonstration, and so on to infinity without any self-evident or first truths (Alvira 36).

So in order to help these philosophers get to the correct idea of God, and everything else too, it is necessary to first fix their theory of knowledge. Strict demonstration is not required to know truth, rather there has to be at least one truth which is known spontaneously. Even Descartes has to recognize this when he doubts everything except what is sure to him. When he is conscious of this or not I am not sure, but he bases all his other knowledge on the fact that he is sure that he thinks. This is not even a strict demonstration, but spontaneous knowledge.

So, again, there must be at least one which is known spontaneously. This fundamental truth is not proved by any other truth. Each person naturally sees the truth that I exist, and in relation to the world that exists by which one naturally forms the Principle of Non Contradiction. So this truth is necessary to accept, otherwise one does not know anything at all. And in accepting this truth, it is clear that truths other than that of strict demonstration can be known. The adage is that realism is not strictly demonstrated, but just self-evidently displayed. So when people realize this, and stop trying to do a strict demonstration that one knows that things exist, one can come to accept the reality of being. Then once people accept that they can know things exist, and they can know being, then they are able to ask the why questions. Why do things exist? Also then, as soon as someone excepts being, they are drawn to accept the metaphysical notion of God, because all of finite being points to God as the being who is pure esse, the necessary first existence. 


In conclusion, Gilson in his book God and Philosophy gives a historical and philosophical overview of the Western idea of God. He identifies philosophers from the Ancient Greeks, through Augustine and Aquinas, to the beginning of the Modern world with Descartes, to the contemporary philosophers today. Gilson shows that the height of truth about God was found in the Middle Ages by Thomas Aquinas, improving Aristotle, and holding God as pure act of being and total being itself.


Alvira, Tomás, Luis Clavell, and Tomás Melendo. Metaphysics. Manila: Sinag-Tala Pub., 1996. Print.

Gilson, Etienne. God and Philosophy. New Haven: Yale UP, 1941. Print.