The art and science of the evidence-based opinion

Humans are opinion machines. Here are some rules of thumb to chasten your opinions and help pick decisions that are important to you and the collective well-being…

Recently, I came to the uncomfortable realisation that my opinions drive almost all of my decision-making. Do’oh.

I know that over the years, a set of values and beliefs have glued onto my psyche, primarily uninvited, and yet are ingrained. I am fond of some opinions, some that I don’t like, and a few that are plain scary. 

I have a point of view on most things political, environmental, and, well, everything. 

Opinions are just everyday human existence. It is what we do. We are “in and of this world”, as my wife is fond of saying. 

And in this world, we interact with other people. 

They all have opinions too, and some are forthright with them.

So I have to hold my ground and decide whether that is by agreeing, acquiescing to more assertive personalities, or being that strong personality myself and bruising my way to uphold my view of the universe. 

And most of the time, I do this without evidence. 

In other words, I have an opinion based on feelings, history, conditioning and indoctrination, much more so than on a logic-based examination of the facts. 

Evidence-free opinions are the unavoidable truth of the matter. There’s no point in saying I should be evidence-based or get better at using evidence, even though that would be an advantage. 

The reality is there are too many decisions and situations that we find ourselves in each day. Applying evidence to every choice is too challenging, and our opinion system makes everyday life much more straightforward. 

We can’t live in the world if we’re constantly unable to make even simple decisions. 

The trick is to decide when to become evidence-based. 

What decisions are essential to individual and collective well-being? 

What are the decisions that matter? 

We have a few rules of thumb that help. 

Rules of thumb for the art of the opinion

#1 — the bigger picture

The first is to become aware of the bigger picture. Not for every single decision, obviously, but now and again through the day, it’s worth thinking, well, what’s the bigger picture here? 

A coffee analogy might help.

When ordering a latte in the coffee shop, ask where the barista got the milk? 

How many cows are needed to provide latte on demand? No doubt the cows live far away from the cafe, so what sort of systems are required to safely put that milk in the barista’s hand with a healthy and regular supply? 

Similarly, with coffee. Where do the coffee beans come from? Presumably, different places than the milk. What processes did that coffee go through? It almost certainly travelled. Was it roasted on-site? 

Indeed, what does a raw coffee bean look like? 

Photo by Rodrigo Flores on Unsplash

So think it through to become aware of the bigger picture. 

#2 — pick a consequence

Another rule of thumb is to try and pick a consequence

Imagine what would happen if I made an alternate decision. Such an alternative is called a counterfactual, an action or scenario counter to the facts. 

In the case of the coffee, what would happen if I didn’t buy the latte?

I would feel cranky most of the morning. The coffee shop loses out on business that is unlikely to make or break them or affect the dairymen or the coffee growers in Costa Rica. In other words, next to zero economic consequences. 

To generate a cascade effect, it would take hundreds of regulars not drinking coffee because of a price hike or a COVID lockdown meant they worked from home. 

The consequences of more significant decisions, such as should I buy this car? Should I buy this house? Should I leave this neighbourhood and move somewhere else? These decisions are life-changing, so it is easier to see their broader consequences. 

It is often worthwhile to think about counterfactuals and pick one or two to understand the implications beyond the self.

#3 — what if everybody did it

The third rule of thumb is to extend the consequence of a decision and imagine what would happen if everybody chose the decision

If everybody decided to join me and have a latte to start their day, the consequences would be dramatic. 

Latte-swilling Westerners comprise roughly 10% or so of the world’s population. 

If everybody in the world drank a morning latte, the supply of coffee from growers couldn’t possibly cope with demand. Coffee prices would spike until more land area came under coffee production, assuming land with the appropriate soil and climate was available. 

Coffee plantations and dairy farms would replace other crops. In other words, there’s a large-scale consequence of billions of people being able to access a morning latte. 

#4 — Ask why

The fourth thumb-sized rule is to ask yourself why? 

Rather than walk into my coffee shop and order a latte, I ask myself why? 

And for the latte, there’s an apparent reason. I enjoy my coffee in the morning. It makes me feel good, thanks to the caffeine hit. I have the resources to buy a coffee, the opportunity, and I enjoy the smile on the barista’s face. A coffee means I start the workday with a little more well-being than otherwise. All of those reasons are legitimate. 

But we notice that they’re very personal self-centred reasons — my well-being and not necessarily the well-being of others. 

The barista and the cafe owner are grateful for my custom, but my reasons for having a coffee are mine.

The four ‘rules of thumb’ for the art of the opinion:

  • See the bigger picture 
  • Explore consequences 
  • Ask, what if everyone did it? 
  • Ask why?

It’s all very personal.

Most of our opinions and most of our decisions are personal.

Beliefs are built over our lifetime as a combination of our nature and nurture. We are told what we should believe, and much is absorbed in our existence. 

Ask why a few times makes it easier to see that most opinions and decisions are self-centred and orientated around what is essential for us as individuals. 

Personal makes perfect evolutionary sense. 

There’s nothing particularly wrong or bad about being self-centred, given it is how human beings have become so successful. Focus on self promotes more making to fulfil our basic biology. Our genetic profile and evolutionary history constrain us. It comes with extraordinary capabilities, but it also brings with it consequences. And one of the big ones is that anyone will find it difficult to go against their innate biology. 

‘Asking why’ will lead to personal reasons for decisions and choices. And if choices are made for family or loved ones, that’s a personal feeling too.  

Again perfect evolutionary sense. 

Rules for the healthy sceptic 

#5 challenge opinions, including your own

The healthy sceptic has another rule of thumb to apply: to question everyone else’s opinion and challenge your own.

When in a disagreement over something, almost always that will be another person’s opinion clashing with yours. So the trick is to be sceptical about the other person’s opinion, fair enough. Ask them where the evidence is how they came to that particular belief. But then do the same with your own opinion and ask why you think differently.

Why do I have a latte, and you decide to have a long black? 

What is it that makes that difference? What evidence builds each opinion? 

Perhaps there was no evidence involved. So the sceptic in us should begin to point out the lack of justification for those opinions. Maybe they just are and have come about as a result of your history and your personality. 

This reflection can be quite confronting, highlighting the number of times that we are not using the facts to make our way through life. 

This has consequences if we ask others to use evidence, if we’re asking for evidence-based policy, or if we want to have a more information-driven set of decision tools for managing the world around us. 

#6 Be curious

The last rule, ‘the thumb to rule them all,’ is… to be curious

Ask questions and find things out alongside the filter for scepticism to get to the bottom of things. 

Now obviously we can’t do this for every situation or for every opinion. But go where your mind takes you and run with your curiosity. 

What sustainably FED suggests…

Apply these rules of thumb, and it becomes easier and easier to see where the evidence stops. 

It turns out that the basics, the fundamentals that give us our technology and our societies’ structures, are what we know. But there are many things we don’t know, plus human decision-making is irrational. For example, there’s no such thing as a perfect market or a logical human. 

Before you know it, a few of your long-held opinions weaken and what gran got from her gran is out of date. That particular bottle of milk has gone off. 

Refresh and create some space in your mind for the important things.

Hero image from photo by engin akyurt on Unsplash


Mark is an ecology nerd who was cursed with an entrepreneurial gene and a big picture view making him a rare beast, uncomfortable in the ivory towers and the disconnected silos of the public service. Despite this he has made it through a 40+ year career as a scientist and for some unknown reason still likes to read scientific papers.

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