Sceptical thinking: the five modes of Agrippa

sceptic‘What if?’ These are possibly the most disruptive words in the English language. If ‘why?’ stops us in our tracks, ‘what if?’ fills the mind with possibilities. Politics, innovation, and art would be impossible without ‘what if?’ ‘What if we tried talking, instead of fighting all the time?’ ‘What if we put a computer in the mobile phone?’ ‘What if the natives on Skull Island worshipped a giant ape called Kong?’ Start a sentence with ‘what if?’ and anything can ensue.

‘What if?’ also clutters the mind with troubles and anxiety. ‘What if it rains on the day of our wedding?’ ‘What if there is a God (or a demon!) watching and judging me right now?’ ‘What if I’m wrong about everything I believe in – what then?

‘What if?’ is a semantic stick thrust into a hornet’s nest of possibilities. Endless ideas fly buzzing about our heads, occasionally inspiring us but mostly distracting us from challenges and tasks.

There are numerous approaches one can take to relieving the effects of ‘what if?’ Some people explore meditation. Others deaden their senses with alcohol and drugs. Too many people simply choose to stop thinking. They give themselves over to the tedious routines of life, ‘blink’ rather than think, and select ‘brain off’ entertainment that enables them to maintain a zombified state through evening until sleep claims them. The approach that I recommend is the opposite of this. Instead of thinking less, I believe that we should be thinking more about the possibilities of life, but to do so in a sceptical way, so that we dispel the irrelevant and immaterial ‘what ifs?’ and focus instead on genuinely valuable and thought-provoking possibilities.

In the last post, we explored scepticism as a way of life. This post provides you with a set of thinking tools to help you engage life in a sceptical manner. Learning to live in a sceptical way takes practice, but it is worth it. By learning to think sceptically about things, we are not only better able to identify things that have real meaning, relevance, and value in life, we are enabled to identify the things that lack meaning, relevance, and value, and thereby declutter our minds by setting these things to one side, zeroing in on the things that count.

Decluttering the mind is every bit as valuable as defragging your computer. Decluttering helps you stop worrying about all the meaningless, irrelevant, and absurd thoughts that clog up your mental bandwidth. It gives you space to think. It gives you back your freedom.

The Sceptics identified various ‘modes’, or techniques, for decluttering the mind. This post outlines five modes developed by the Sceptic philosopher Agrippa, who lived in Greece in the 1st or 2nd century AD. We know almost nothing about Agrippa; yet his modes have stood the test of time. Recorded for posterity by Sextus Empiricus, they were embraced with the rediscovery of Sceptic thought in the 16th century to become fixtures of modern thought.


F. Scott Fitzgerald claimed: ‘The test of a first rate intelligence is the ability to hold two opposed ideas in the mind at the same time and still have the ability to function’. This is essentially what is involved in Agrippa’s first sceptical technique, the mode of dispute.

The mode of dispute works like this. Select a position or belief that many people accept as true (something worth arguing about, like ‘Abortion is always wrong’, ‘God exists’, ‘Human C02 emissions are warming the planet’, or ‘Capitalism and democracy go hand in hand’).

Now identify some arguments for and against this position. Select the strongest arguments pro and contra. It may help to write these arguments on a piece of paper. Lay the arguments out as clearly as you can and reflect on the strengths and weaknesses of each of them.

This may take some time. No one said thinking was easy.

It is vital, at this point, that you avoid leaping to a conclusion for or against these arguments. If you find that you want to leap to a conclusion, ask yourself why this is. Are you harbouring some implicit prejudice or belief? Keep an open mind. Hold to the process of sceptical reflection.

In the end, you may decide that one or other line of argument is irrefutable. In this case, you should accept this position as one worth adhering to. A good sceptic respects sound logic and the weight of evidence. Just be sure that your judgement is based on solid reasoning, not on some vague intuition you have or the emotional appeal of the arguments. In the majority of cases, you’ll find that there are valid points on both sides of the debate, or that it is impossible to make a judgement on the basis of the given evidence. If there are solid arguments pro and contra a position, you should suspend judgement on it. In a word: be sceptical.

Don’t listen to people who say that you’re being difficult – you’re not. When it is impossible to make a rational judgement on an issue, suspending judgement is the most reasonable thing to do.

Carnaedes applied the mode of dispute in his speech to the Roman senate. Contrary to popular belief, Carnaedes’ goal was not to infuriate the senators, but to force them to acknowledge that they didn’t really understand justice as well as they thought they did. If you can lead people to see that they don’t understand things as well as they think, you can help them shift to a more thoughtful and inquiring state of mind. This creates the opportunity to engage the matter in a deeper way. The danger, as Carnaedes discovered, is that you infuriate people in the process.

Infinite regress

The second sceptical mode is the infinite regress. This is an extremely powerful sceptical technique. Applied effectively, an infinite regress can demolish a point of view like dynamite in the foundations of a house. You set up an infinite regress by showing how a position or belief logically depends for its support on a more basic position or belief, which itself depends on an even more basic position or belief, which depends for its support on another position or belief, and so on.

How many arguments are susceptible to this mode of critique? All of them. In the history of philosophy, there has yet to be found a single position that does not logically depend on an infinite string of prior (unstated) positions. This either means that all knowledge is without foundation, or that the foundations of knowledge and belief are not logical per se, but practical and conventional (a ‘form of life’, as Wittgenstein claimed).

Which is the correct view? I’ll leave it up to you to make the call.

puzzledIf you are a parent, chances are you’ll have been subjected to infinite regress reasoning before. Children love trapping their parents in the logic of regress (‘Why does Daddy go to work every day?’ ‘Daddy has to earn money’. ‘Why does Daddy have to earn money?’ ‘Daddy earns money to pay for the house and everything’. ‘Why do we need the house and everything?’ ‘Because … it’s time for bed’). Applying this technique properly, however, requires you to do more than just repeatedly ask ‘why’? The art of setting up an infinite regress is to identify the unquestioned presuppositions implicit in a position or belief, and to bring them to light in such a way that each attempt to defend the belief reveals another set of presuppositions.

The French philosopher Rene Descartes famously developed an infinite regress argument to sceptically critique his own beliefs. In The Mediations (1641) Descartes took a sceptical approach to the knowledge of his own existence. By teasing out and sceptically addressing his implicit beliefs concerning how he knew the world existed, Descartes came to the conclusion that the only thing he knew for certain was that he was thinking. ‘I think – therefore I am’, Descartes announced. Yet, even this conclusion involves an unquestioned supposition. Can you see what it is? Once caught in an infinite regress, it can be hard, if not impossible, to escape.

Unproven hypothesis

The third sceptical mode is useful when you are debating with someone who is aware of the holes in their argument and has made an effort to cover themselves. If the interlocutor is any good, they’ll have probably made a pretty good case. But it is unlikely that their argument is watertight. The mode of unproven hypothesis involves looking for the leaks.

You set about the approach as if you were preparing to set up an infinite regress. Push you interlocutor to acknowledge the implicit presuppositions in their position or belief. Allow them to backtrack as far as they want to go down the chain of supporting arguments and look for the point at which they stop. You can usually tell when people have their backs against the wall because they start being aggressive and demeaning, saying things like: ‘Well, everyone knows that X’ or ‘You’d have to be stupid not to appreciate Y’.

Don’t be cowed by this behaviour. Go in for the kill. Your interlocutor has seized on a basic belief that they’re hoping no one will question. This is their unproven hypothesis. Call them out on it. ‘Well, that’s your hypothesis. Is it really unquestionable, or are you just assuming it is?’ Your interlocutor is standing on a false foundation and they’re just about to fall through the floor.

People who cling to unquestioned hypotheses are teetering on the edge of an infinite regress. You can push them down the rabbit hole by pointing out how the basic belief that they take for granted logically depends on a prior set of beliefs. Down they go. If your interlocutor refuses to acknowledge the weakness of their argument, spell it out for them. Articulate their presuppositions. You are doing them a favour by disrupting their illusions of a foundational belief.

Descartes’ famous conclusion ‘I think, therefore I am’ harboured an unquestioned hypothesis that Descartes himself refused to acknowledge. Descartes thought that he was being rigorously sceptical in his approach, yet, when he drew his conclusion, he assumed that every act of thought implies a metaphysical identity, and ‘I’ that does the thinking. On the basis of this hypothesis, Descartes reasoned that thinking implies being, and thereby claimed: ‘I think, therefore I am’.

As Nietzsche and others have pointed out, the link between thought and identity is by no means certain. ‘A thought comes when it will, not when I will’, Nietzsche claimed, his point being that thinking often occurs independently of our conscious intent and volition, and to this extent, shouldn’t be seen as a product of the self. The physical process of thinking and the processes involved in creating a personal identity, while related to one other, are by and large distinct. Logically speaking, there is no necessary reason why we should assume that thinking implies the existence of personal identity. Descartes was guilty of mobilising an unquestioned hypothesis.

Relativity of judgement

It is vital to keep in mind, when applying sceptical techniques, that the point of the exercise is not to win arguments and take down your opponents, but to test beliefs with the aim of determining whether or not it is possible to suspend judgement on them. To live a sceptical life, you should try to suspend judgement as many beliefs as you can. This is how you achieve peace of mind, which the Sceptics called ataraxia: freedom from mental disturbance.

The fourth sceptical mode applies to a specific kind of position or belief, where the ‘reality’ or ‘true nature’ of things is invoked. People seize on these kinds of positions all the time. Sometimes they are frank about it, saying: ‘This is how things/people really are’. Other times, they employ euphemisms like: ‘When it comes down to it…’ or: ‘At the end of the day…’. It amounts to the same thing: the appeal a privileged insight into the nature of things.

homoeconomicusIn the face of these kinds of arguments, the Sceptic refers to the relativity of judgement. This involves pointing out that views on ‘reality’ are perspectives that often say more about the perceiver than the perceived. Consider the reality of the physical environment about you. Chances are it’s full of things like walls, floors, chairs, tables, and so on. Are these things ‘real’? We tend to accept that they are. But this reflects a culturally and linguistically determined perspective on these objects. From the perspective of a bat, they are solid shapes registered through the reverberation of sound waves. From a scientific perspective, they are energy condensed to a slow vibration.

Which is the ‘true’ perspective on reality? The Sceptic does not deny that a true reality may indeed exist, but on account of the relativity of judgement, they claim the most reasonable position is to suspend judgement on what this is. There is always more than one way to look at an issue. By pointing out how different perspectives reflect different ways of experiencing the world, Sceptics are able to deflate claims to ultimate knowledge and affirm the plurality of being.

Circular reasoning

The final sceptical technique is to identify circular reasoning. In this case, the Sceptic looks for arguments that beg the question, assuming what they mean to prove.

The classic example of circular reasoning is the argument against revealed religion. ‘How do I know God exists? It says so in the Bible’. Of course, if God did not exist, there’d be no reason to believe what it says in the Bible. This argument presupposes what it means to prove, assuming the existence of God and using this as justification for believing the letter of the Book.

Nationalistic arguments commonly employ circular reasoning. Take a claim like: ‘Australia is the best country in the world. We have an excellent climate, great beaches, and a laid back lifestyle’. The assumption here is that an excellent climate, great beaches, and a laid back lifestyle are things that make a country great. From a certain perspective (say, a surfer’s perspective), this seems irrefutable. But it is a case of relative judgement. By positing a set of relatively valuable features as proof of national excellence, the argument assumes what it means to prove. What it really says is: ‘My country is the best in the world because it has features that (I believe) make it the best country in the world’. Logically speaking, it loops back around and eats itself.

The five modes of Agrippa are guidelines for critical thought. Even if you’re not ready to pursue a sceptical lifestyle, they are excellent tools for sharpening the mind and keeping your opponents on their toes. Keep in mind that not everyone appreciates having their beliefs tested in public (as Socrates found out), so you may want to venture your critical reflections gently.

Cluttered minds are quick to anger. Handle them with care. Focus on decluttering your own mind.


  1. Although in some sense this is a bit off topic, but also completely relevant to the various themes that you cover on your site please check out the various essays available on this site. Essays which give a unique perspective on the paradoxical state of the humanly created world in “2013” .
    The authors book Coming Into Being is superb.

  2. Thanks for the reminder, just before the holidays when discussions can get overheated, to unclutter and clarify.

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