Reason Alone?

Many people are very willing to champion the importance of reason and rationality, but this can be very similar to praising motherhood and apple pie: few people defend unreasonable or irrational behaviour.  I hear people advocate for rationality - but in my experience, it is quite rare to hear them say whether our actions should be based on reason alone, or if reason should be used alongside something else - and, if so, what.

Ayn Rand famously championed 'absolute reason', and she is not alone; it is not hard to find people and groups prepared to argue for the sole primacy of reason.  To give just one example: "Knowledge is lucid and can only be formed by the use of reason. There is no other path. Reason is absolute." [1]  Romanticism was a reaction to the emphasis on science and rationality produced by the Enlightenment - the Romanticists rejected the popular belief in  reliance on reason alone.

This issue has been explored in many works of fiction.  In one of the  best-known examples, Mary Shelly's Frankenstein, the creature is produced by science, but we see both the creature and its creator being driven by passion.  And in Metropolis, the classic film by Fritz Lang, we see a society ('the Hands') ruled by reason ('the Head'), and the result is efficient but brutal.  The film's message, "The Mediator Between the Head and the Hands Must Be the Heart", has been dismissed as trite - but 'trite' simply means that the message is obvious and uncontroversial.  For many people, it is obvious that feelings are also important, that reason must be moderated by compassion and morality.

Guided by Science?

In talking about the way the UK government responded to the Covid-19 pandemic, the Prime Minister repeatedly claimed that "at all stages, we have been guided by the science".  This claim is not only false, it is a dreadful and absurd idea.  It is also a common technique, used by people to avoid taking responsibility for their decisions.  Science does not tell us what to do, it only tells us what can be done.  "We are simply following the facts" is a manifest impossibility: facts are statements about the past, about what has been, but a plan tells you how to create something in the future.  You need an intention to build or a desire to possess something which does not currently exist: what you intend to create is not yet a fact.

Neither science nor reason can guide anything, from individual choice a national strategy. If you can provide an objective, a context, a set of resources and a metric, then science and reason can (possibly) tell us the best way to achieve the objective.  Science can tell us the fastest (or the cheapest, or the most energy efficient) way to get from A to B, but it cannot tell us whether we should go there. It can tell us the likely consequences of an action, but it cannot tell us if the action is good, kind or loving.  Reason can often tell us how to do something, but it cannot tell us if we should do it.  Science and reason were vital tools in working towards the Millennium Development Goals [2], but setting and agreeing the goals was mainly a combination of morality and politics. 

Science, reason and rationality deal with facts, with what is, but they cannot give us a single moral principle; in addition, they cannot give us a goal to aim for, or a purpose to live for.  As the saying goes, "you cannot derive an 'ought' from an 'is'."  And the inability of science and reason to speak about any of the things that matter to us as human beings is not just an issue about the origin of morality, value and purpose - reason can't even be used to justify Rand's fixation on selfishness: to make selfishness a reasonable strategy, you have to add in a whole bunch of beliefs about the world, about the functioning of social organisms, and about human nature.  And if you want to promote your choice of a particular set of beliefs, as Rand does, you need a stronger argument than 'they seem reasonable to me'.

Reason and ... what?

The Framework used on this web site is helpful here, distinguishing between particles, people and purpose.  As we say, each of these areas requires the use of a distinct set of tools and disciplines.

  • When we are talking about particles - and things like them - then science and reason are the tools to use.  Science gives us laws which - with an astonishing level of precision and regularity - tell us how the physical world operates and enables us to predict thousands of years into the future.
  • But when we are talking about people, and living creatures in general, things are different.  Our bodies follow the laws of science, but what we do with them is another matter.  There are common topics which we recognize; the basics of survival, sustenance and sex are fairly universal, but these common concerns work themselves out in uncountable and frequently unpredictable ways.  Social animals care about things like status, reputation, respect, cooperation and intimidation.  We can study the behaviour of living creatures and seek to understand them, in subjects such as biology, psychology and sociology, but this understanding has to be expressed in terms relevant to living creatures (such as 'safety' and 'status'), which simply cannot be expressed in terms of the activity of atoms and molecules.
  • And when we come to consider issues such as purpose, things are different again: the disciplines which work when we are seeking to understand the observable activity of living creatures are not able to help us here.  Ideas and beliefs are the subject matter of philosophy and religion - which does not mean that reason needs to be thrown out of the window, only that it operates in a different way when dealing with a different subject, and things it deals with are not the subjects which are considered in the physical sciences.

In each of these areas, reason alone is insufficient to tell us anything: reason always needs material to work with.  In physics, reason deals with things like mass and energy; in biology, reason deals with things such as risk and mate selection; in philosophy, reason deals with things like existence and morality.

It is tempting to say that reason needs facts to work with - but in each area, what we consider to be 'the facts' change and develop with time.  In science, new discoveries contradict (or, at least, modify) previous certainties: we believed Newton's laws for a long time, but they turned out to be close approximations to the truth when you restrict your interest to certain parts of reality; General Relativity and Quantum Mechanics both appear to be true, but contradict one another.  What we consider to be scientific truth is only a hypothesis which has not yet been falsified.  When you apply reason to mistaken ideas people wrongly consider to be facts, you are unlikely to get a good result.  In the world of computers, there is an acronym which summarises this nicely: 'GIGO' - Garbage In, Garbage Out.  We are less able to apply reason to the real world than most people think.

And remember: even if we were able to apply reason to the real world in a reliable way, a great many people think that compassion and morality should influence our behaviour, as well as reason.

The Limits of Reason

Reason is not only limited by our understanding of the world we apply it to; reason itself is limited.

The study of reason is called 'logic'.  There are numerous kind (or 'systems') of logic, such as Aristotelian and Boolean.  In general, systems of logic work very much as you might expect while they are purely abstract systems, but various problems arise as soon as you attempt to relate the logical system to the real world - or even when you attempt to create a purely abstract system which comes close to being able to describe the real world in a meaningful way.

In particular, problems arise when the system accommodates infinity (important when you are dealing with Mathematics) or self-reference (important when you use language and try to think about the meaning of words, also important in Mathematics when dealing with set theory), or the system attempts to be complete.  There is also the irritating observation that an attempt to test the truth of two statements which are logically identical can be very different in the real world [3].

In Principia Mathematica [4], Russell and Whitehead attempted to derive Mathematical truth from a few basic axioms (statements they considered to be self-evidently true) and logic, while avoiding the pitfall of self-reference (easily seen in Russell's Paradox - if you construct the set of all sets which do not contain themselves, does this set contain itself?)  but the attempt was not successful on either front: avoiding the problem of self-reference became unworkably complicated, and some 20 years later, Kurt Gödel demonstrated that the attempt was doomed to failure: in any consistent system, there must be true statements which cannot be proved [5].

It turns out that we are not good at identifying what is 'obviously' true.  Around 300 BC, Euclid created the formal discipline of Geometry by identifying a few 'obviously' true axioms (or 'postulates'), and using them to prove a large number of geometric propositions.  For around 2,000 years, almost everyone who thought about these things believed that Euclid's geometry described facts about the real world - facts which Euclid had proved, and anyone who studied him could prove for themselves.  Then some Mathematicians started to play around with alternatives to one of the axioms (the 'parallel postulate'), and created other self-consistent geometries [6].  Then Einstein came along, and pointed out that the universe we live in is not Euclidian, after all.  None of the Geometry you learned at school is actually true in the real world - it's just a close approximation when the lines you draw are short enough.

The Use of Reason

Reason is limited.  We care about things which reason can say nothing about; reason can only work with information which can be wrong or misunderstood; reason itself is flawed and incomplete; and reason fails to handle the real world, the one we are seeking to reason about.  But this does not mean that reason is useless, only that it is not omnipotent.

There are many areas of life where we need to apply reason, where we need to identify the facts (as best we can) and form a rational response to those facts.  Climate Change is one obvious example.

But reason and rationality are not enough.  People do not deny Climate Change because the evidence is unclear or the reasoning unsound.  There are probably many reasons: the probable consequences of our activity are too horrible to contemplate; they are too attached to their standard of living and cannot face the changes which will be required; it is far more comforting to listen to the voices who point out that people have been prophesying disaster since the beginning of human civilization; and so on.  The reasons are emotional, and social and cultural, and probably many other things.

We need reason.  But the most important thing we need is not a better grasp of reason, but a better grasp of when and how to use reason, and what else we need to bring to bear alongside reason, in order to address the massive problems this world faces.



(This article started as a response to the post about Ayn Rand and Objectivism.)



[1]  From the article about 'Reason' in the Importance of Philosophy website (

[2] The Millennium Development Goals were agreed by the United Nations in 2000 (

[3]  The two statements, "All swans are white" and "All non-white things are not swans" are the same, from a logical perspective, but one is a statement about all swans (which could potentially be verified), and the other is a statement about every non-white object in the universe (good luck with verifying that).

[4]  An outline of Principia Mathematica which helpfully abandons the original notation is provided by Stanford University (

[5]  The 'Incompleteness Theorem' is surprisingly easy to understand in outline (ödel).

[6]  The 'parallel postulate' says that there is precisely one line which can be drawn through any given point which is parallel to another given line, although it can be stated in a number of (surprisingly different) ways (


[See also Reasonable Misdirection.]


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  • Paul

    Perhaps our understanding is convergent, but not able to completely align.

    You say to me: “I think that you, like me, believe that human connection and compassion should shape our beliefs, as well as Reason.  But, in that case, you don't believe in 'reason alone' any more than I do”. Yes, I think you are right about what I believe. Perhaps the distinction is that Reason should be the underpinning of things that matter in terms of our and humanity’s well-being, and for determining Absolute Truth  (whether mathematical or philosophical or theological), whereas emotion provides colour and makes the whole thing worthwhile. I don’t use Reason when I am in an art gallery, or looking at a country landscape. I don’t use Reason as the basis for deciding to indulge in gliding and other aviation-related hobbies; I love the open spaces and there is a human desire to soar: but I do use Reason to assess the risks involved. I didn’t use Reason when deciding who to marry: perhaps I should have done, things might have been smoother subsequently, but I think I would have regretted it if I had never had the experience of a romantic relationship, even if those feelings don’t last for ever. I would use Reason for arguing with a flat-earther: they have become the cliché for the obviously faulty use of reason in the same way that the Nazis are the cliché for evil.

    It doesn’t help that the English language can be ambivalent, especially with words such as “believe” or “I’m sure”. You say that you wouldn’t say that you [only] “believe” that two plus two equals four [because you know it]. I do use the word “believe” in that way, meaning that I am satisfied that it is provable logically and mathematically and is an Absolute truth at least in the Newtonian universe, but I also use the word in the other sense, meaning: “I believe the kebab shop is open until 11pm (but I’m not sure)”.

    The elephant in the room in all this is the implications for religious faith. To me, belief in any kind of supernatural can at best follow from belief in the second sense that I defined above (because we can’t see or measure the supernatural). Your first example is valid: I have faith that if I get on the bus, the driver will take me to where Google Maps says they will, because this has almost always worked in the past. But can that be applied to religion? Does prayer get answered? I cannot be sure that if I trust in God I will not die of cancer or get killed in a car crash, because this has happened to some Christians that I know. So what use is a belief in God here on earth, and can this be extrapolated to certainty about an afterlife? Maybe religion is not about our needs but about making the world a better place (the bible pretty much says that), but do we need formal religion for that? I will admit that sometimes situations which might have become a problem for me have turned out very well in a way that I could interpret as miraculous. Maybe I am merely detecting a pattern and ascribing meaning to it, but there is something in me which doesn’t want to be ungrateful to God if he is looking after me. (I could tell a story illustrating this at one of our meetings). But if he is looking after me, why are some other people’s lives so disastrous?

    This brings us back to the Sovereignty question and I will think more about that last bit when I reply to your last post on God’s Sovereignty. I would agree that Christianity is more Rational and less weird than most other religions, but questions remain. Christians have worked very hard at providing logical reasons why the Resurrection “must be” true, and done a good job, but questions remain, quite apart from theological disputes about the meaning of the Cross and Resurrection (Propitiatory Substitutionary Atonement vs “God showing His Love”).




  • Adrian,

    Okay, you may have a point about the Incompleteness Theorem.  Although, in my defence, I only suggested it is 'surprisingly easy' to understand.  I suppose it depends on how easy it is to surprise you...

    I think we are all trying to make sense of the world around us - it is often a confusing place.

    I'm not sure how to understand your claim that Reason is only the “least worst” option for determining Truth and Belief, when you tell us this is not what you actually do in practice, and it doesn't even seem to be what you want to do.  I think that you, like me, believe that human connection and compassion should shape our beliefs, as well as reason.  But, in that case, you don't believe in 'reason alone' any more than I do.

    You talk about believing in something provable - isn't that a contradiction?  For me it is - I would not say that I believe two plus two equals four.  But perhaps we are using language differently here?

    And you talk about believing in things that do not need to be accepted by faith - again, I think we have a very different understanding of the nature and role of faith in human life.  When you get onto a bus, you don't know where it will go, but you have faith the driver will take you along the expected route.  When you get married, you do not know if the relationship will work out, but you have faith that you will each keep the promises you make.  All the important decisions in our lives are fundamentally questions of faith - what do you believe is the right thing to do, or the best thing for you and those you love?  Which is not to say that reason has nothing to do with these choices, but reason is (as I am arguing here) only one part of a larger picture.  Maybe an important part - but certainly not the whole picture.

    I need to keep this short, so just one other brief comment: over the years, I have put quite a lot of work into Christian apologetics, and (while it is not impossible) you would find it hard to find a Christian who is trying to prove their religion.  I certainly was not trying to prove that Christianity is true.  What I was trying to prove is that some forms of Christianity are reasonable - and they appear very reasonable when you compare them against the blind faith required by other belief systems.  I invite people to consider questions of evidence, and compare the various alternatives.  And I have never claimed that other holy books - or other books of any kind - are not inspired at all.  But the question of what we mean by 'inspiration' is probably getting too far off topic...

  • Paul 

    I think I am right in remembering that your degree was in Mathematics and Philosphy, which explains why you suggest that Godel’s Incompleteness Theorem is easy to understand! I am afraid that I am more of an amateur in these things, and much of what I am saying in these discussions represents my own attempts to make sense of it all and work out what I do think and what I can justify believing, or not believing.

    Perversely, my attraction to Reason and Rationalism, of the Enlightenment and of Ayn Rand’s Objectivism, is probably not entirely driven by Reason, but by my desire to be able to believe in something provable rather than something that needs to be accepted by faith or by my feelings: so a psychological or even spiritual need. On the other hand, I do like Art, which exercises my spiritual side and/or the right side of my brain: primarily Modernist Art but also Romantic Art, which as you say was a reaction against pure Reason. But then, Rand was not against Art, though she saw Abstract Art as decadent (I quite like it), and so championed something called Romantic Realism: I have been unable to work out from her writings a precise definition of this. Many of the decisions that I make in life are down to what I happen to like: whenever I spend money on something that I don’t actually need, I am not applying reason.

    So again I come back to the conclusion of Reason being only the “least worst” option for determining Truth and Belief. Faith, whether in a Religion or in believing what you want to believe such as Trump winning the 2020 election, depends on even more axioms. People of faith tend to take as axiomatic that their God exists and that their Holy Book is inspired by God and other religions’ aren’t. A very small proportion of people of faith think much about apologetics, trying to prove their religion, and at least they should be respected for trying. Even Richard Dawkins has said that the Argument from Design is a strong one. I don’t particularly want to get into knocking Religion, except that it seems an obvious example. But Reason can lead us into conclusions that we do not like. As I write this, the Conservative Party is choosing a new leader. Not being a party member and never likely to be, I won’t be voting for any of them. But I lean toward Richi Sunak because he is not promising tax cuts straight away. I would like there to be tax cuts, and for wages to increase: but Reason says the country cannot afford it. The national debt is into the trillions, largely due to Covid spending which Sunak concluded was justifiable at the time and some Conservative Libertarians called him a socialist for trying to help people: but now there is no more money. Likewise. I don’t like the implications of the need to tackle climate change, but it will be unreasonable not to.

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