What Are The Five Ways of Thomas Aquinas?


Perhaps the most popular set of arguments for the existence of God are Thomas’ five ways:

The proof from motion, the proof from causality, the proof from the contingency of the world, the proof from grades of perfection, and the proof from finality.

It’s important to keep in mind that these five ways (found in Part I, Question 2, Article 3 of his Summa Theologica) are intended to be a summary, not an exhaustive treatise, of what Thomas thinks are the most convincing arguments for God’s existence.

It’s also worth noting that theists (believers in God) are not bound to think the arguments convincing; as if God’s existence somehow depended upon the irrefutability of Thomas’ arguments.

In fact, if there is an argument for the existence of God more popular than Thomas’ five ways it would have to be the ontological argument, first formulated by Anselm of Canterbury, an argument which Thomas rejected!

In my experience, many Christians have heard of Thomas’ five ways, they have a vague recollection of what they might be, but many have not read what he actually wrote. They are often surprised then to find them quite pithy.

So, on this, the feast of St. Thomas Aquinas, do yourself a favor and read, not a commentary of the five ways – you can read this great one later later – but the five ways written by the man himself:

The First Way – Proof From Motion

The first and more manifest way is the argument from motion. It is certain, and evident to our senses, that in the world some things are in motion.

Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act.

For motion is nothing else than 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 be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold.

It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another.

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, and that by another again.

But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand.

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 – Proof From Causality

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 it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate 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 in efficient 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, to which everyone gives the name of God.

The Third Way – Proof From Contingency

The third way is taken from possibility and necessity, and runs thus.

We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these always to exist, for that which is possible not to be at some time is not.

Therefore, if everything is possible not to be, then at one time there could have been nothing in existence.

Now if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing.

Therefore, if at one time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence—which is absurd.

Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their

necessity caused by another, as has been already proved in regard 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.

The Fourth Way – Proof From Grades of Perfection

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 different ways something which is the maximum, as a thing is said to be hotter according as it more nearly resembles that which is hottest; so that there is something which is truest, something best, something noblest and, consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaph. ii.

Now the maximum 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.

The Fifth Way – Proof From Finality

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 move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer.

Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

14 thoughts on “What Are The Five Ways of Thomas Aquinas?

  1. Thank you Matt for this article, this is great! Just wanted to point out that the link from amazon seems broken, I can’t open it! But maybe it’s just me.

    God bless!

  2. Great article. Aquinas is as equally timely as he is timeless.

    If you’d be so kind, Matt, could you help me by either letting me know or giving me direct sources as to what kind of counter-argument non-theists use to try to deny the validity of these arguments?

  3. I think the 5 ways are a bit dated as ‘proofs’ for a god, especially with what we have learnt in quantum physics and biology.

    The First Way – Proof From Motion
    The Second Way – Proof From Causality
    The Third Way – Contingency

    Unfortunately things evident to our senses isn’t a good way to determine things when we encounter the very big (universe) or very small (quantum physics)

    Causality isn’t as concrete as we first thought. A causes B causes A has been shown by physicists. This is a flaw in Aquinas’ thinking. There was no way he could of known, Humans didn’t even know about quantum physics at that time.

    See: http://phys.org/news/2012-10-quantum-causal.html
    See: http://en.wikipedia.org/wiki/Retrocausality

    The Fourth Way – Proof From Grades of Perfection
    This doesn’t lead to a good god or any god. The same standard could be applied to evil and the most evil being. “There is evil in the world, and the fact that we can perceive different standards of evil means there must be some maximal exponent of evil, and we call this supreme evil God.”

    We can also apply it to a sandwich. “There are tasty sandwiches in the world, and the fact that we can perceive different standards of taste means there must be some maximal exponent of taste, and we call this the supreme tasty sandwich.”

    Even if this argument wasn’t flawed and was completely true, it doesn’t support the God of the Bible.

    The Fifth Way – Proof From Finality
    Evolution shows this to be false. Completely natural processes has created every animal on Earth without any intervention.

    So while in Aquinas’ day the 5 ways would of been a good apologetic, this is no longer the case.

    1. The thomistic proofs are commonly misunderstood to be predicated upon temporal causality. But really, that is not necessary. The quantum examples you gave did not challenge causality but only uni-directional causality. But even with this simplified version of causality, an uncaused cause still results logically.
      A good reading of Matt Frad’s recommendation: Edward Feser’s Aquinas may help to clear up these misunderstandings. And hopefully to distinguish between the misleadingly similar first three ways.
      The fourth way doesn’t apply to evil since evil is in fact not another “good” or a counter-good like salt to pepper, but is an absence of good, so cannot be used in terms of perfection. As to sandwiches, your example is misleading, since it is clearly subjective. However, the conclusion could be drawn that there exists a maximum form of pleasure.
      And the fifth way is unshaken by evolution, as are final causes. But this, like all of these arguments, are based on a solid understanding of Aristotle, and should not be taken just like that. The Summa was just a foundational textbook, sketching out the basics, and was not meant to be taken as a comprehensive explanation of the proofs.
      If you really want a solid, detailed explanation of what Aquinas actually meant, try Feser’s Aquinas, or even, if your feeling adventurous: The Last Superstition (also Edward Feser)

      1. First causality, this paper http://www.nature.com/ncomms/journal/v3/n10/full/ncomms2076.html which the news story comes from is questioning causality. However since it hasn’t been shown in nature I will argue the next point. Even if there is some uncaused cause the uncaused cause doesn’t logically fall to a god.

        Evil is not an absence of good. If I decide between donating to a charity and buying book is buying a book evil because it is an absence of a ‘good’ action, Of course not. If I decide between donating to a charity and burning down the same charity and stealing the money one action is good and one is evil. One is not the absence of the other.

        Anyone who eats this sandwich will agree it is the perfect sandwich. So it isn’t subjective.

        Evolution is a natural, unguided process which has no evidence to show it was created by a mind and it does shake the fifth way. You would need to give evidence of how this process was created by a mind.

        St Thomas Aquinas (or anyone else) couldn’t even show a mind can exist outside a biological organism.

        The 5 proofs should be able to stand on their own and they don’t. The new authors that write about the proofs try and repackage them in a modern way.

        Even if each of the 5 proofs were correct there is no logical way to show that the god still exists. It could have been consumed during The Big Bang.

      2. “The 5 proofs should be able to stand on their own”… Indeed they should, but in their full form, not in an easily misunderstood form like the above. It is an extremely cut-down version written for an overview, and not a thorough explanation of what they are. A more expanded version can be found in the summa contra gentiles. Or in any of the books I mentioned.
        Theology isn’t simple. You won’t be able to just disprove Aquinas in a few paragraphs… you actually have to understand what he meant, and then try and debunk it. Otherwise you’re just fighting a straw man, Dawkins style.
        “It could have been consumed during The Big Bang”… I rest my case!

      3. You could try to address my points. Just saying I have it wrong isn’t a very good way to show Aquinas proofs are true.

      4. Fair enough. I’ll do my best, but you should really do some research!

        First there is a distinction between actuality and potentiality. Actuality is what something is, and potentiality is what it has the potential to become. For example, an ice cream is actually an ice cream, but has the potential to be melted into a lump of goo. Things in the universe constantly move from actuality to potentiality. This is known as change. However, something can’t move unless it is moved by something else. That something else can’t be nothing, since from nothing nothing comes (a quantum vacuum is btw by definition not nothing, but a quantum vacuum. It is a material state, and is therefore metaphysically something). This creates a chain of efficient causes.

        Say I had a book. You want that book. But I don’t have it, I got it from a friend. He doesn’t have it, he got it from a neighbour. Etc. Ad infinitum. Now that chain is like the chain of existence, or actuality. You can’t have existence, unless you were given it, and if everybody was always borrowing it, then nobody actually has it, and you and I could not exist. Therefore there must exist something that is, in and of itself, pure actuality, or an uncaused cause. To get from an uncaused cause to God is not the subject of the five ways, but is explained elsewhere. A little sample:

        Since it is an uncaused cause, it isn’t effected by other causes, and is therefore unrestricted, or in-finite. This doesn’t mean some silly notion of expanding for ever like an ever-growing substance, but merely that is un-constricted. Multiple unconstrained beings could only be differentiated by their differences, or restrictions, and therefore could be multiple in-finite things. Therefore God is one.

        As you can see from the above, this stuff isn’t simple, and shouldn’t be treated as such. Aquinas never meant for people to cut the five ways out of the Summa like a fish out of water. It is based on a complex, heavy, and well argued metaphysics, that should not be ignored.

        Evil is a perversion, or twisting of good. It is not something in itself. An illustration between this might be shows when contrasting good and bad habits. A bad habit, such as being lazy, is the lack of a positive action. Whilst a good habit, like getting up when one should, is a positive action in itself. Not giving money to a good charity is not a positive act, but can still be regarded as evil. Burning down a building is a removing of the “goodness” of the building, so to speak, and not constructive in itself. It is therefore not a positive act, but a counter-positive act. A distortion, or lack of goodness.

        Sandwiches are material, whilst goodness is more of a formal “cause” (in the sense of the four causes), so does not come under the “jurisdiction” of the argument, so to speak. To understand more, try reading about Aristotle’s distinction between form and matter. I am not prepared to argue all of the five ways in full here, as that would be doing it a disservice.

        As one progresses down the “ways”, one has to take into account more and more metaphysics. The fifth way is dependant upon final causes, which simply state that something, be it physical or biological, moves towards some kind of end, of it’s nature. Evolution does not contradict this.

        As to the Thomistic explanation of what a mind is, you are confusing it some what with the Cartesian notion.

        I’ll leave it at that. I’m not prepared to write a book. If I have shown anything, I have hopefully illustrated that Thomism is not some 1 page theory, but a very complex series of conclusions based on Aristotle’s metaphysics. In this case there are no short-cuts. So either you stop attacking straw men, and perhaps go read Craig’s Kalam cosmological argument instead, or otherwise go and read Feser, or the summa contra gentiles, or even Aristotle. This is heavy, complex stuff, and should not be treated otherwise.

      5. Thank you for your polite reply.

        Metaphysics is a difficult area because you can’t really demonstrate it. No one can effectively show the metaphysical equivalence of nothing. We don’t know if the metaphysical definition of nothing is even possible or makes sense.

        You present a false dichotomy with good and evil. Not every action is good or evil. Some actions are neutral. If I decide to read a book or use a computer which of those actions are good and bad (positive or negative). Neither are good or bad. Both are neutral. We could use your example of habits if one of my habits is to put socks on before my shirt or my shirt on before socks is either of those actions good or evil? This would make good and evil separate entities.

        The Theory of Evolution does not have an end it is a process. If we use the process itself as evidence isn’t the circular?

        A process exists
        A mind needed to create the process
        Therefore a mind created the process

        If in Craig’s Kalam cosmological argument we assume there an uncaused cause there is no reason we can’t equally assume a god or the singularity existed in a eternally stable state.

        I want to thank you again for taking the time to reply. I will take a read of Aquinas more deeply in the future.

      6. Thank You.

        As to metaphysics being unknowable, I disagree. But luckily in this example, I only have to explain the distinction between nothing and a quantum vacuum. A quantum vacuum is something. It is a material state. But when Craig says nothing, he really means nothing. No-thing. Not a presence, but a complete lack of presence. The thing about contemporary physics is that while it is frequently misunderstood to contradict Aristotelian metaphysics, it’s really just a misunderstanding of the metaphysics that leads to the supposed contradictions.

        Good and Evil: The distinction between putting your socks on first and putting your shirt on first, although morally equal, are not morally neutral. They both are work towards the action of getting dressed. However, not putting your socks on would make the action of getting dressed incomplete, and therefore “evil”, so to speak. A good table is a table that fulfils the form and purpose of a table. So a table is missing a leg, and falls over is an “evil” table, so to speak. As you can see, the Thomistic idea of Good and Evil is much more pervasive than simply pertaining to actions.

        There are many ways to mistreat somebody, but only one perfectly good way to treat them…

        The explanation of final causes, although not affected by the theory of evolution, are not explained by them either. This explanation is, once again, based on Aristotle’s metaphysics.

        I was a little confused by what you implied was a circular argument. It does not in fact seem circular, except that you have the major and minor premises the wrong way round. Additionally: This argument seems to correspond more to Paley and Craig’s Argument from design, which are quite different from the fifth way.

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