Aquinas Explainer: The Fifth Way

Warning: amateur philosophy ahead!

Aquinas’ Five Ways arguments for the existence of God are usually misunderstood nowadays. It’s not so much that they are complicated; rather, because they are so different from modern Western thought, it takes a little while to wrap your head around them.

Most people assume his argument from design (the Fifth Way) is a god-of-the-gaps argument that has been refuted by evolution. Not only is that not the case, but the argument cannot possibly be refuted by any scientific theory. To find out why, read on.

Imagine if you will, a group of scientists performing an experiment on water. They heat the water but instead of boiling at 100 degrees as expected, it boils at 75 degrees.

What caused this to happen? The scientists may consider the following:

– Something is wrong with their equipment
– There are impurities in the water
– Igor swapped the water with vodka again
– Under a specific set of circumstances previously unknown to science, water boils at 75 degrees

And here are some options the scientists will likely not consider:

– The water is conscious and sabotaging our experiment
– Glitch in The Matrix
– Water changes at random and just doesn’t make sense. Who can understand it?
– Water has stopped working. Guess we can’t drink it any more
– Looks like water is taking Tuesdays off
– Water has changed by decree of the secretive Water Committee. It will now boil at a lower temperature than what it used to

Why don’t the scientists consider the second set of options? It is because the natural world is extremely regular and predictable. If it wasn’t, science would scarcely be possible.

It is this regularity about nature that Aquinas is trying to explain.

Water being water, it has properties such that when it is heated to 100 degrees it boils. In Aquinas’ metaphysics, this means water has an essence that includes being internally “directed to” boil under the circumstance that it is heated to 100 degrees. This is called “intrinsic teleology”. “Teleology” meaning that it points to an end goal, in this case that of boiling at 100 degrees. “Intrinsic” because it is part of its internal nature, rather than being imposed by any outside forces.

Anything science can tell us can be described in this way. All material things, because they are what they are, can be described as having an essence, that is internally “directed to” behave in certain ways, in a predictable fashion that can be studied by science.

That’s all background. While it is part of Aquinas’ metaphysics it is not part of the Fifth Way and stands or falls on its own merits.

The Fifth Way

But why do things have this intrinsic teleology? It didn’t have to be this way. In an alternate universe, perhaps nature would behave in an arbitrary fashion which is not predictable, follows no rules and cannot be studied by science. Since logically nature could have been arbitrary, there must be a reason for why is isn’t.

Aquinas argues that since natural things are “directed to” their ends, and that they predictably meet those ends, this can be compared to arrows that always meet their targets. Arrows that always hit the bulls-eye tell us there is an archer. Likewise, since natural things are always “directed to” their ends, this is by design. But natural things don’t have intelligence, so they can’t be their own designer. “Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.”

Does evolution show that the Fifth Way is wrong? No, because evolution is simply natural things behaving in a predictable way just as Aquinas is describing.

What are the alternative explanations? Some might say that nature “just is” predictable and that there is nothing to explain, but I don’t think this will do. A policeman who discovered a dead body would not assume that it “just is” there with no need to investigate further. You can’t just assume that something requires no further explanation; you have to prove that.

I think the Fifth Way is still a good argument which deserves consideration and is not hard to understand once you understand the background assumptions.

There is a lot more that could be said here, much of it above my pay grade. There are further details, arguments, counter-arguments, counter-counter arguments, counter-counter-counter arguments and so forth, all in copious amounts beyond what any person could reasonably want, for philosophy is a bottomless pit.

For more information on the Fifth Way, this blog post is externally “directed to” provide you with the following links:


Can evolution justify human knowledge?

While science tells us a lot about the universe in which we live, it is built on a number of assumptions. One of these is the validity of human logic. Does the human capacity for abstract thought allow us to learn the truth about the world? Since science assumes that it does, it cannot give us a non-circular answer to this question. Nevertheless it may still be worth asking what support, if any, science offers for this idea. Specifically, can the theory of evolution give us confidence in human cognitive faculties?

It has been argued by some philosophers, such as Richard Swinburne, that since natural selection acts for advantageous behaviours rather than correct logic, that there is no reason to believe that natural selection has selected for abstract thought. The usual response to this is that brains that think correctly will over the long run be advantageous and thus selectable, even though survival does not always correspond to correct logic. I’m willing to assume that’s true; to me, it seems plausible enough.

Does that mean that the knowledge problem is solved? Perhaps not. There are two reasons to doubt this. 

First: we are the only species, as far as we know, that has the capacity for abstract thought. 1 is a very small sample size on which to base conclusions. We can’t really know empirically that evolution is good at producing abstract thought without being able to study it in other animals. If there were 20 or 30 other species with this capacity, we could make that assessment, but we don’t have that luxury.

There are currently 10 million species of animals on this planet and 5 billion that have gone extinct. If I took 5 billion attempts to get my first hole in a game of golf, I wouldn’t brag about my golf game.  It looks as though evolution is terrible at producing abstract thought and we are just a freakish coincidence.

Second: Even if we assume that natural selection can and will do the job, it will still do that very slowly. So if it takes 5,000,000 years to evolve abstract thought, we might only be 25% of the way through the process. In other words, it might take 2 million more years before humans stop thinking like jellybrains and there’d be no way for us to know.

Far from providing support for the human capacity for knowledge, then, evolution widens the problem from a gap to a chasm. There is no respite from the human knowledge problem here.


Goldfish Science

In the past, I have argued that there is no such thing as 100% confident human knowledge. Everything that we know comes laden with assumptions. There is no way around this.

Part of this is the question: How do we know that the human mind works? That human logic works? That science, which depends on human logic, also works?

While science must assume that science is possible and therefore cannot prove that, it does not follow that science cannot give us any confidence at all in our own abilities. In fact it has done just that: the astonishing successes of science and the groundbreaking technologies based on them have given those of us in the Western world immense confidence in our own brilliance and the brilliance of science.

The potential problem here can be shown using an analogy: goldfish science. Imagine a goldfish tank with a handful of goldfish, some pebbles and a novelty plastic castle. Goldfish Science believes that the entire world is made out of plastic castles. The evidence? That plastic castle in their fish tank! Also, goldfish can push the pebbles together to make castle-like structures. So the theory is proven, not just by the evidence but also by its practical usefulness.

Obviously this is terribly stupid, but who will tell the goldfish? Other goldfish certainly can’t. To be truly confident in their science, the goldfish need a superior intelligence to vet it for them.

It is highly likely that our science doesn’t have the extreme credibility problem that goldfish science has, but this doesn’t rule out more subtle problems. Until a superior intelligence vets our science for us, there will always be a reason to have doubts about the scientific project.

Paley’s Revenge

William Paley presented an argument for intelligent design using the watch analogy. It went like this: Imagine you found a watch lying on the ground. You would conclude based on its complexity that it had an intelligent designer. Given that plants and animals are far more complex than watches, it is reasonable to conclude that they too had an intelligent designer.

Nowadays this is considered as the ultimate god-of-the-gaps argument. Because evolution was then a “gap” in scientific knowledge that has since been filled, so the story goes, this design argument has been answered.

This is a prime example of the dangers of basing philosophical positions on science. You just never know when the gaps will close. (Or when they will open, which is possible due to the provisional nature of science. People forget that part.) If you want to argue God’s existence, then, stay away from arguments based on “gaps”.

Let’s rephrase Paley’s analogy for our modern evolution-knowing times, just to see if we learn anything.

It is 2050 and Paley is the first explorer to visit Mars, when he sees a watch lying on the ground. He picks it up in bewilderment. But as he keeps exploring, he finds a lot more watches in a vast variety of types and styles. He gets a team in and they investigate in earnest. He finds the remains of long-dead watches buried deep in the rocks. Some of them have little resemblance to the watches on the surface. As he travels to other parts of the planet, he finds watches of different varieties again. Slowly he comes to an astonishing realisation: the watches are all descendants of a common ancestor, changing into other types of watches over time! Somehow the watches are able to just change by themselves with no watch designer, driven by competition of different watch types against each other. There is nothing to it except lots of time, the watches somehow “finding a way”.

“As if!”, cried a disbelieving world as they read Paley’s report. But as the evidence came in, it soon became undeniable. As astonishing as it was, it was true. Slowly but surely, the world swallowed it’s incredulity and moved on, a few diehards excepted. But there was still much work to be done as the details of what was happening were yet unknown.

Years went by. Generations passed. Watch-evolution, far from being novel, was now part of the scientific furniture when Paley’s great-great-grandchildren finally pieced together the internal mechanisms of the theory. They found that the watches were not simply changing of their own accord. Rather, the change was enabled by the replication system within each watch. This system had been there since the first watch and had barely changed. In effect, what was happening was not types of watches turning into each other, but one watch system expressing itself in a trillion different varieties.

I wonder what Paley would have made of that?

Life truly is more strange, subtle and wonderful than anyone could have imagined.

You can’t prove anything

You can’t prove anything.

You can’t prove the world is real. You might be dreaming or hallucinating or in The Matrix.

If the world is real, you can’t prove that your senses are telling you the truth about it. Or that your mind is.

You can’t prove that I am conscious. On the outside it looks like it, but on the inside I might be just a void.

You can’t prove that what’s worked for you in the past will keep working for you tomorrow.

You can’t prove that the past ever happened. (Try going there to check.) You can’t prove that your memories are accurate.

You can’t prove that the people of the future won’t look at us as monsters because of what we do. Or as gods.

You can’t prove that the author of this blog intended it to mean what you think it means.

You can’t prove you won’t be hit by a bus tomorrow.

You can’t prove your wife truly loves you.

You can’t prove that everyone isn’t laughing at you behind your back. You can’t prove they’re not out to get you. You can’t prove they won’t be waiting for you when you get home.

You can’t prove your wife isn’t one of them.

You can’t prove that there isn’t a massive government conspiracy that has concocted all the conspiracy theories so as to make anyone who uncovers their conspiracy look silly, and that’s why conspiracy theories are so ridiculous.

You can’t prove that God exists. You can’t prove that the Scientologists didn’t get it right. Or the atheists. Or the good folks at ISIS.

You can’t prove that any of the following are real in any sense: free will, meaning (as in purpose), meanings (of words), your mind, morality, mathematics.

You can’t prove that your modern Western mindset isn’t acting as a sort of ideas cage, preventing you from seeing the truth.

You can’t prove that human logic works. You can’t prove that this sentence makes sense. You can’t prove that “this sentence” makes sense.

You can’t prove that your mind would have passed quality control at a mind factory.

You can’t prove that the world makes any type of sense at the most basic level.

You can’t prove that science tells you the truth about the world. (It assumes much of the above.)

You can’t prove that any scientific theory you can think of won’t fail a replication study tomorrow, or be contradicted by new evidence.

You can’t prove that science tells us about all of reality. (“Science tells us about all of reality” is not a scientific hypothesis.)

You can’t prove that if super intelligent aliens landed tomorrow, they wouldn’t dismiss our science and mathematics as being limited or wrong or missing the point somehow. (“Your pathetic human languages do not allow me to express the depth of my contempt for your stupid ideas”, says Zxxcxcc from the planet Kvzzxrrk. [1])

This is why some people go insane.


[1] I was granted an audience with Zxxcxcc the other evening. “You humans are so ridiculous” he said, his eye pulsating as he twirled his antennae with his left trunk. “You vote for people you know are idiots, but you still think you have the intelligence to unravel the deepest mysteries of the cosmos.” 

No Virginia, There Are No Aliens

Many people believe in the existence of extraterrestrial life. The reasoning is quite simple: Given that we evolved on this planet, and there is such an enormous number of other planets, galaxies and stars out there, surely extraterrestrial life exists on a number of these planets? However, this is based on a number of dubious assumptions that fall apart when subject to examination.

Recently in the New York Times, Adam Frank claimed using the Drake equation (that calculates the number of active, communicative extraterrestrial civilisations in the Milky Way galaxy) that at least a trillion alien civilisations have existed. [1]

Taking that number at face value for a moment, let’s add another variable to the Drake equation: What is the probability that an active alien civilisation will do or have done something that allows us to verify their existence? Even if the probability is only one in ten million, that means we have verified the existence of 10,000 alien species already! The reason you and I don’t know anything about this? Obviously a CIA plot!

If that reasoning seems dubious to you, congratulations: you have become appropriately sceptical about probability calculations that pull numbers out of nowhere.

One of the biggest assumptions made when using the Drake equation is that all the steps involved are possible. If any of the steps involved are impossible, the number of alien species you get becomes zero, because zero probability multiplied by a billion trillion gazillion is still zero.

This includes the possibility of life evolving from non-life. How do we know that is scientifically possible? “But we got here!”, I hear you say. But that is merely assuming what you are trying to prove. Consider string theory: if you pointed out it has no evidence and someone said “But we have gravity and string theory explains gravity!” what would you say? It is not enough to aim to explain something: you have to show evidence you actually do. Abiogenesis is just another scientific hypothesis like any other: we should not be assuming it’s true unless there is a solid body of evidence to say so.

A statement of the problem

The theory of evolution describes a system of life that is responsible for all the diversity of life that we know. While the life forms that it produces change dramatically over time, the system itself is remarkably stable, barely changing since the beginning. For it to work, this system contains the right amount of flexibility to accommodate change, not so little that it would stagnate and not so much as to collapse.

The DNA system of life is shared by all life as far as we know. No other system of life has ever been observed.

If evolution describes a system of life, that makes abiogenesis the search for a system that produces systems of life – a system that, beginning with whatever was available in Earth’s early days, would produce the system of life that we are all familiar with. Like evolution, this system would have to have a core of stability as it produced the life-system of evolution, else it itself would collapse before it got the job done. Unlike evolution, it would not be able to use natural selection over a large part of the process.

A model of abiogenesis that is not in fact a system, but a large number of ad-hoc steps, stretches credulity and becomes far more difficult to prove.

Comparisons between evolution and abiogenesis inevitably bring out the difficulties of the latter. Evolution started with observations of Galapagos island finches and other animals. Abiogenesis started with nothing but the idea of abiogenesis. Evolution was figured out by a handful of scientists in the 1800s. Abiogenesis has hundreds of scientists investigating it. Evolution had a clear starting point. Abiogenesis could have started with a warm pond, thermal vents, one of Saturn’s moons or who knows where else. Evolution had the fossil record providing a plausible map to guide research. Abiogenesis doesn’t. If evolution research is like navigating a maze with a map, abiogenesis is like an indeterminate number of mazes, with no map, which might be 3D mazes, and you’re blindfolded.

Unlike evolution but like string theory, abiogenesis researchers are focussing on finding a plausible model of abiogenesis first and proving it actually happened later. String theory shows the downside of this approach. Plausibility does not imply actuality and a theory of abiogenesis that has plausibility only will be no better off than string theory.

The discussion so far shows the extreme difficulty involved in proving any theory of abiogenesis; certainly, thus far scientists have not come up with a single plausible model. Most hypotheses of abiogenesis are considered dubious in the extreme; most scientists in the field feel that the ‘RNA World’ model, that proposes an RNA replication system as a halfway point to the DNA system, is by far the most promising.

The ‘RNA World’ model has it’s critics, however. It has been criticised as ‘almost unfalsifiable’ and ‘full of holes’, even compared to a ‘creationist mantra’ (hardly a compliment in mainstream biology!)[2]. Certainly the problems involve seem quite daunting. If the ‘RNA World’ model is the best there is, yet ends up collapsing under the weight of it’s problems, perhaps it will be time to give up on abiogenesis altogether.

But wait: “Just because abiogenesis hasn’t been proven yet, doesn’t mean it never will!” you might respond. Of course that is true, but there is still a problem here – this attitude makes abiogenesis unfalsifiable.

Falsification and the limits of science

Scientific theories are supposed to be falsifiable because science can only make progress by discarding theories that produce no evidence. That is how science is supposed to work. In practice, falsification (or verification) of a theory takes a long time. This is because after a failed experiment, rather than abandon the theory, scientists will usually tweak it and try again. It is only after many such tweaks that scientists will draw a line under a theory and move to something more promising.

For a theory of any complexity, if you were so inclined you could simply keep tweaking and tweaking and tweaking forever, never giving up, as there is always a chance you are giving up too soon if you don’t. This makes falsification almost a pragmatic decision. It has been found that scientists are reluctant to consider a theory falsified unless there is an alternative. If no alternative has been presented, they will simply keep tweaking away.

This introduces a danger. Because of the philosophical presuppositions of most scientists in the Western world, they may be inclined to give abiogenesis much more time than it deserves, as there is no obvious scientific alternative to it. Given the huge amount of time and effort already spent investigating abiogenesis, we might be there already or well on the way.

The modern West assumes that given enough time, science can do anything. But there is no basis for assuming this. Science is a human activity; therefore it is limited by human brainpower and human technology. So even if you grant that science can answer all questions in principle, it does not follow that it can do so in practice.

When science was younger, scientists answered the low-hanging fruit questions that were easy for science to answer. As science gets older, the remaining questions will get more and more difficult and eventually only the impossible ones will remain, at which point science will become a bit like philosophy, running around in circles. I think we’re already there in some fields. I expect to see articles about the stagnation of science within 20-30 years.

If abiogenesis is not in fact an impossible question, it sure is acting like one. How you interpret that ultimately depends on the philosophical assumptions you bring to science, rather than the science itself. What is clear though is that making assumptions based on the viability of abiogenesis is unwise, being unsupported by evidence.



Cosmological Argument

A few notes on the Cosmological Argument for the existence of God:

We start by asking ourselves: what things need a cause?

  • Anything with a beginning needs a cause
  • Anything that is changeable needs a cause
  • Anything that is divisible into parts needs a cause (to explain how the parts came together)
  • Anything that is contingent needs a cause. (Anything that could be different to how it is now or could possibly not exist)

Does the universe needs a cause? Apparently so because:

  • There is strong scientific evidence that the universe has a beginning, and
  • Additionally it is contingent, changeable and divisible into parts

If the cause of the universe itself has a beginning, or is changeable etc, it too will need a cause. Since an infinity of physical things is impossible, or leads to absurdities, we need a First Cause to kick things off.

Since this First Cause has no beginning, doesn’t change, is not divisible into parts and is not contingent, not only does it not need a cause – in principle it cannot have one.

Since all material things have beginnings and are contingent, the First Cause must be immaterial.

This everyone understands to be God.

Objection: A multiverse could be the First Cause


  • If the multiverse has a beginning, or is composed of parts or is contingent, it itself will need a cause

Objection: The universe could just “be”, as a causeless brute fact

The difference between God and the universe in this respect is that the universe seems to need a cause whereas God does not.

This idea of a brute fact is awful, because:

  • It violates all logic. When policemen stumble across a dead body, they immediately start seeking a cause. No-one ever considers the possibility there won’t be one.
  • There is nothing about the “brute fact” concept that there should only be one. So why don’t we see things popping up out of nothing all the time?
  • If there is only one “brute fact”, this requires that the first matter that kicked off the universe to be “special” somehow, with some kind of magical power to cause itself.
  • Overall, a horrible idea: worse than magic, because at least with magic you have a magician.

Objection: We can’t use causation logic beyond the physical universe

Because it goes beyond what we can see with our senses, using metaphysical causation logic to get a First Cause is invalid.


  • Why not? Feels like an excuse to avoid dealing with the logic involved.
  • Does this mean that outside the universe, logic itself breaks down somehow? Truth because false, 2+2=5?
  • If the argument here is that reality in itself is different to reality as it appears to us, how do we know we can trust any human ideas.
  • Many scientific theories are quite bizarre to the senses and common sense. Should we discard those also?
  • When this argument is used for atheism rather than agnosticism, it assumes what it’s trying to prove. It would make more sense to use this argument to argue that if God exists, He is unknowable.

Objection: A First Cause is not the same thing as the God of any specific religion


  • Is is easy to get from First Cause to a God who is immaterial, omnipresent, all-powerful, etc. One day I might edit this post to show how! Some ways to do so may be obvious to you if you think about it for a bit 🙂
  • I can’t speak for other religions, but Christian philosophers have always acknowledged that while the First Cause is compatible with the Christian understanding of God, it is not possible to prove Christianity using philosophy. So if you are afraid of acknowledging the validity of cosmological arguments because you don’t want to become a Christian, relax! You don’t have to.

Objection: This doesn’t prove that God exists as it does not provide empirical evidence.


  • This is a logical argument, not an empirical one and it should be evaluated on that basis.
  • Science is built on logic and not the other way around.
  • If it can be proved logically that God must exist, than surely He must exist, even if we do not yet have empirical evidence. This is because science cannot contradict sound logic. If you think otherwise, please design a science experiment to test that true statements are false or that 2-5=-1.

Objection: Only things that can be shown by science to exist actually exist.


  • This is self-defeating: The idea that only scientific things exist cannot be shown by science itself; this idea is philosophy, not science.
  • Science studies the material world. Since God is immaterial, using science to argue the non-existence of God is like using a metal detector to argue that non-metallic objects don’t exist. Simply put, science is not the right tool for the job.
  • If only scientific things exist, here is a short list of things that apparently don’t exist: God, mathematics, logic, morality, consciousness, truth, abstract ideas, your sense of self, meaning (as in purpose), meaning (of words), the soul, good and evil, philosophy, beauty, free will.

Objection: Since time and space both started at the Big Bang, a cause of the Big Bang would have to be before the beginning of time, which is impossible.


  • A cause of the Big Bang could be outside of the time-space continuum; perhaps in another time-space continuum or outside of any time at all.
  • What makes a cause a cause is not that it comes before in time, but that it does the causing. (Apologies for lame wording here!) For example, if you had a time machine and used it to punch someone 50 years in the past, you would still be causing that punch even though you are doing it from the future.

Objection: A “block universe” would remove the need of a First Cause

If you don’t know what a block universe is, go here: Eternalism (philosophy of time)


  • Assuming the “block universe” is real and therefore the universe has no beginning and doesn’t change (itself a controversial point), a first cause would still be required due to the “block universe” being contingent.

Objection: Quantum physics shows that things can come into existence without a cause


  • It is true that particles come from quantum fields, but what about the fields that generate the particles?
  • There is no such thing as a “scientific nothing” as “nothing” simply means “not anything”. If there isn’t anything, there isn’t anything for science to study, is there?

Objection: Radioactive decay shows that things happen without a cause


  • The fact that there is a scientific theory that describes radioactive decay shows that it is not entirely random. Therefore any logic regarding causation still applies.
  • What a nuclide decays to is predictable – for example uranium-234 always decays to thorium-230
  • While the timing of decay of a single atom cannot be predicted, we can still measure half-lives for large numbers of atoms