Deconstructing 5 Logical Fallacies to Enhance Your Cognition

Logical fallacies and cognitive biases are embedded into every facet of our daily lives, yet most of us are unaware of their pervasiveness or consequential effects. Equipping yourself with this knowledge can be empowering and a source of a ‘competitive edge’, both personally and professionally.

This is an original, introductory article I wrote on the topic — hopefully the first of many. Feel free to share this with any of your friends or work colleagues you think may be succumbing to these human blind-spots!


Adopting a rational and logical approach to thinking versus relying on one’s empirical and intuitive senses is not an either/or dilemma (an early introduction to a logical fallacy). It is quite possible to demand a high level of evidential proof whilst simultaneously leveraging one’s desires for creativity and spontaneity. A rational framework can provide a useful filtering mechanism for such creativity.

The building blocks for separating useful information from useless information is the ability to identify fallacious arguments. The following 5 logical fallacies are some of the most common relied upon by people (usually unconsciously and ignorantly):

Logical Fallacies

1. Sunk-Cost Fallacy

Sunk costs are costs already invested into something which cannot be recovered, and are therefore of no relevance to future decision-making.

“I have already spent four years of university studying Biochemical Engineering, why would I change industries now and ‘waste’ these last four years”.

Instead of focusing on the four years already invested in a Biochemical Engineering degree, I should consider this in the context of the rest of my career. Four years represents 8% of a prospective 50 year working life. It would be much better for me to pivot now, even if I have already invested four years of time (not to mention the skills I have acquired which are likely transferable across domains). Even though it would have been better to pivot after two years instead of four, pivoting after four years is better than trying to do so after 20 years. Time, like money, can be compounded so the earlier you ‘cut your losses’ and pivot elsewhere, the greater the scale-ability.

The same principle applies to investments in the stock market, years spent in a relationship, deposits paid for a holiday. People tend to throw good money after bad money. Costs or investments don’t just entail money either — it could be your time, happiness, health, well-being etc. Even the intellectual energy invested in a particular opinion or point of view can block us from being willing to change our minds, leaving us exposed to dogma and ideology.

The biggest impediment to avoiding the sunk-cost fallacy is pride and perspective. It requires a great degree of humility to admit that one is wrong and to cut losses as soon as one becomes aware of the error.

The opposite of a sunk cost is a prospective cost, which is an avoidable future cost. These should be taken into consideration when making future decisions.

2. Zero Sum Fallacy

This fallacy assumes that one person’s success must come at the expense of another’s loss.

“If my colleague gets the job promotion ahead of me, I stand to gain nothing”.

Incorrect. Your history of working with your colleague on various projects and your interpersonal relationship means that they will likely refer more work to you and involve you in interesting projects in their new position. The pie is very rarely divided 0:100. It is usually a variant shared ie. 60:40.

Donald Trump regularly applies this fallacy, particularly when it comes to trade. In his eyes, if China are ‘winning’ (say through the acquisition of new jobs) it means that the USA must be ‘losing’. This assumes that there is a finite number of employment opportunities in the world. This is not the case. The number of jobs in an economy are not fixed. Furthermore, at a higher level of abstraction, China’s increased employment may stimulate greater consumer demand for products made in the USA. Most trade deals, or any kind of co-operative relationships, are mutually beneficial. This is especially so given how interconnected our globalised world is, and the network effects that this brings.

The core fallacy of zero-sum thinking is the belief that all resources are finite. Zero-sum thinking promotes competition and division instead of co-operation. With many things in life it is not ‘one or the other’ but ‘as well as’.

“A rising tide lifts all boats”.

3. Ad Hominem Fallacy

Where someone attacks the character or attributes of a person rather than engage with the substantive ideas being debated.

“John is a Republican voter. His views on climate change are irrelevant”.

The implication here is that John’s political affiliation determines the legitimacy of his climate change arguments. The same principle could be applied to John’s skin colour, sexuality, gender and so on (which we see happening all the time). Each of these domains must be viewed in isolation, at least when considering John’s views on climate change. I would need to fact-check John’s denials about climate change and present him with statistics and evidence that prove otherwise. Dismissing John’s claims on the basis of his political affiliation — or any other categorisation — is intellectually weak and does nothing to add credibility to the opposing argument.

People often dismiss a person’s ideas because they deem them to be a ‘bad’ person. Martin Heidegger was one of the greatest philosophers of the twentieth century but he had a very unfortunate affiliation with the German National Socialist Party, before eventually seeing the light and renouncing these views (whatever his motives for doing so may have been). Some people would argue that any idea of his does not deserve consideration or a public platform. However, on a first principles basis, the legitimacy or value of an idea should be view as distinct from the person putting forth the idea. These should be considered separately, unless there is a direct and causative relationship between the idea and the person’s beliefs.

For example, the way to defeat a white supremacist (at least intellectually) is not to call him a “racist” or a “fascist” — even if this is factually true — but to present objective evidence as to why the idea of there being a superior race is devoid of any scientific, biological or anthropomorphic basis. There is zero percent chance that calling someone a racist will alleviate a situation and improve their perspective. Quite the opposite. They will become defensive and closed off to intellectual correction.

Engaging in ad hominem arguments is a race to the bottom. Don’t mistake the messenger for the message.

4. Ad Populum / Consensus Fallacy

The argument that something must be true because a significant or a majority of people believe it to be true. Groupthink.

Before Copernicus, Galileo and Kepler came along in the 16th century and presented their paradigm shifting discoveries, the strong likelihood is that nobody who had ever lived until that time believed that the Earth rotated around the Sun. However, as we now know, the belief of the majority was not representative of physical reality.

A majority approval may be evidence that something is valid, but it does not prove that it is valid. This is often how people attempt to frame this fallacy. Majority approval is instructive, but not conclusive.

The key takeaway is to question everything. Many of the beliefs and presuppositions we take for granted are derived from authority, tradition or popular belief. If we dig a little further and investigate the basis for these assumptions, they may prove to be irrational.

If someone tries to convince you on the basis that ‘everyone else is doing so’, demand a stronger rationale.

5. Correlation / Causation Fallacy

‘Correlation does not imply causation’ means that an apparent relationship between two things does not necessarily prove that a direct causal relationship actually exists.

Mistaking correlation for causation leads to ‘false positives’, where we interpret a cause where there is none. This is often seen in the reporting of health studies, where a correlative trend is interpreted or portrayed as a source of causation. The problem with this is that we then intervene in a situation where there may be no need to do so. Nassim Taleb calls this iatrogenics, where an intervention causes more harm than benefit. This can range from doctors over-prescribing medication or surgical procedures to Central Bank economists artificially injecting capital into an economy, affecting the self-correcting mechanisms that are often in-built in robust and organic systems (whether that is the human body or the free market).

We are blinded by the anthropomorphic bias through which we view the world, believing that humanity has mastered nature. This leads to a hubris that our interventions in ecosystems will play out in accordance with our predictive analysis, whilst failing to consider the potential unintended consequences of our actions, whether they are benign or not.

This is not to say that we should ignore correlation completely. Far from it. Correlation suggests a causal relationship, which then requires further investigation. Otherwise we run the risk of having ‘false negatives’, failing to identify a causal relationship where one actually exists by mistaking the absence of evidence for an evidence of absence.


These are merely five of many logical fallacies that inhibit human rationality. Knowing about them doesn’t necessarily mean that you will automatically refrain from succumbing to them, often unconsciously so, but you can begin to identify their use both by yourself and by other people in everyday conversations (which can be quite an exhilarating experience). This ability will allow you to de-bunk false arguments and equip yourself with a stringent filtering mechanism for determining legitimate arguments.

Exploring nuanced crevices of truth in a world of complexity. Aspire to provide readers with better epistemic frameworks for intellectual and moral progression.

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