Thomas Aquinas, “The Five Ways” The Argument with Analysis

This translation is from the Summa Theologiae of St. Thomas Aquinas, Second and Revised Edition, translated by Fathers ofthe English Dominican Province,1920. This translation is now in the public domain. The analysis of the argument whichfollows is © 2004 Theodore Gracyk and is used with attribution.It is often assumed that the Ways are meant to be self-sufficient proofs, which is something of a mistake. Thomas intends theWays to cogently describe, as he puts it, “what all people mean when they say ‘God.’” These Ways are how God can bemeant, when the term God is spoken of by reason alone. Thomas does not, in fact, believe that complete knowledge of God ispossible without recourse to revelation, that is, by special knowledge of God given by God and God alone. But RomanCatholic “natural theology” following Aristotle, holds that natural human reason can know that God is, apart from revelation(or “revealed theology”). To know what or who God is, of course, requires religious knowledge which comes from divinerevelation. So it is important to understand what the Five Ways are, and what they are not. It has also been noted that they aremeant to be taken together; no one of the arguments is particularly convincing by itself.The Ways are taken from Aristotelian science as found in the Physics and Metaphysics, as well as the formulations ofMaimonides in the Guide to the Perplexed and ibn Sînâ’s Arabic commentaries on Aristotle (both profound influences onThomas’s thought). Thomas uses them for his own religious purposes, of course, but they are not strictly original to him. Theyare legitimately associated with him, however, because of the profound impact his discussion of them has had on subsequentphilosophy, and also because it was Thomas that organized them into their present form and who collected them together intoone place.I have interpolated below reference to Aristotle’s own arguments to show Thomas’s source, so that you can see theAristotelian origin of the Five Ways (something all too many thinkers ignore or sometimes even deny, oddly), and also so thatyou can see how Thomas explicated them in his own terms.From Summa TheologiaePart one, Question 2, Article 3The existence of God can be proved in five ways.The first and more manifest way is the argument from motion. It is certain, and evident to our senses, that in the world somethings are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is inpotentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing elsethan the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality,except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to beactually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality andpotentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentiallyhot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thingshould be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion byanother. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, andthat by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, noother mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staffmoves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by noother; and this everyone understands to be God.[“Substances are the primary reality, and if they are all perishable then everything is perishable. But motion cannot be eithergenerated or destroyed, nor time…And there is no continuous motion except that which is spatial…and circular…Thereforethe ‘ultimate heaven’ must be eternal. And since that which moves while itself moving is intermediate, there must be a firstmover that is not itself moved.” (Aristotle, Metaphysics 1071b-72a)]The second way is from the nature of the efficient cause. In the world of sense we find there is an order of efficient causes.There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so itwould be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in allefficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of theultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause is to take away the effect.Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. But if inefficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect,nor any intermediate efficient causes; all of which is plainly false. Therefore it is necessary to admit a first efficient cause, towhich everyone gives the name of God.[Aristotle’s “first mover that is not itself moved” (prôton kinoun akinçton) is not only the source of motion, but the source ofsources; that is, along with being the unmoved mover, it is the uncaused causer. All causes require a cause (there are no causalloops and no infinite causal chains, according to Aristotelian physics). And this, Thomas says, is what “everyone gives thename of God.”]The third way is taken from possibility and necessity, and runs thus. We find in nature things that are possible to be and not tobe, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it isimpossible for these always to exist, for that which is possible not to be at some time is not. Therefore, if everything ispossible not to be, then at one time there could have been nothing in existence. Now if this were true, even now there wouldbe nothing in existence, because that which does not exist only begins to exist by something already existing. Therefore, if atone time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even nownothing would be in existence–which is absurd. Therefore, not all beings are merely possible, but there must exist somethingthe existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it isimpossible to go on to infinity in necessary things which have their necessity caused by another, as has been already proved inregard to efficient causes. Therefore we cannot but postulate the existence of some being having of itself its own necessity,and not receiving it from another, but rather causing in others their necessity. This all men speak of as God.[“That which has potentiality may not actualize it. Thus it will not help if we postulate eternal substances…unless there be inthem some principle which can cause change. And even this is not enough…for unless it actually functions there will not bemotion. And it will still not be enough even if it does function, if its essence is potentiality, for there will not be eternalmotion, since that which exists potentially may not exist. Therefore there must be a principle of this kind whose essence isactuality.” (Aristotle, Metaphysics 1071b)]The fourth way is taken from the gradation to be found in things. Among beings there are some more and some less good,true, noble and the like. But “more” and “less” are predicated of different things, according as they resemble in their differentways something which is the maximum, as a thing is said to be hotter according as it more nearly resembles that which ishottest; so that there is something which is truest, something best, something noblest and, consequently, something which isuttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaph. ii. Now themaximum in any genus is the cause of all in that genus; as fire, which is the maximum heat, is the cause of all hot things.Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection;and this we call God.[“But since there is something, X, which moves while being itself unmoved, existing actually, X cannot be otherwise in anyrespect…Thus X is necessarily existent; and as necessary it is good, and in this sense is a first principle. For ‘the necessary’has all these meanings [including] ‘that without which excellence is impossible’… Such then is the first principle upon whichdepend the sensible universe and the world of nature. And its life is like the best that we can enjoy only temporarily, but itmust be in that state always.” (Aristotle, Metaphysics 1072b)]The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies,act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result.Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot movetowards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its markby the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being wecall God.[“We must also consider in which sense the nature of the universe contains the good or supreme good; whether as somethingseparate and independent, or as the orderly arrangement of its parts. Probably in both senses, as an army does; for theefficiency of the army consists partly in the order and partly in the general; but chiefly in the latter…all things, both fishes andbirds and plants, are ordered together in some way…everything is ordered together in one way.” (Aristotle, Metaphysics1075a)]Gracyk’s Analysis:The First Way: Argument from Motion

Our senses prove that some things are in motion.Things move when potential motion becomes actual motion.Only an actual motion can convert a potential motion into an actual motion.Nothing can be at once in both actuality and potentiality in the same respect (i.e., if both actual and potential, it is actualin one respect and potential in another).Therefore nothing can move itself.Therefore each thing in motion is moved by something else.The sequence of motion cannot extend ad infinitum.Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God. The Second Way: Argument from Efficient CausesWe perceive a series of efficient causes of things in the world.Nothing exists prior to itself.Therefore nothing is the efficient cause of itself.If a previous efficient cause does not exist, neither does the thing that results.Therefore if the first thing in a series does not exist, nothing in the series exists.The series of efficient causes cannot extend ad infinitum into the past, for then there would be no things existing now.Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God. The Third Way: Argument from Possibility and Necessity (Reductio argument)We find in nature things that are possible to be and not to be, that come into being and go out of being i.e., contingentbeings.Assume that every being is a contingent being.For each contingent being, there is a time it does not exist.Therefore it is impossible for these always to exist.Therefore there could have been a time when no things existed.Therefore at that time there would have been nothing to bring the currently existing contingent beings into existence.Therefore, nothing would be in existence now.We have reached an absurd result from assuming that every being is a contingent being.Therefore not every being is a contingent being.Therefore some being exists of its own necessity, and does not receive its existence from another being, but rather causesthem. This all men speak of as God. The Fourth Way: Argument from Gradation of BeingThere is a gradation to be found in things: some are better or worse than others.Predications of degree require reference to the “uttermost” case (e.g., a thing is said to be hotter according as it morenearly resembles that which is hottest).The maximum in any genus is the cause of all in that genus.Therefore there must also be something which is to all beings the cause of their being, goodness, and every otherperfection; and this we call God. The Fifth Way: Argument from DesignWe see that natural bodies work towards some goal, and do not do so by chance.Most natural things lack knowledge.But as an arrow reaches its target because it is directed by an archer, what lacks intelligence achieves goals by beingdirected by something intelligence.Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

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