Don’t Ask The Barber if You Need a Haircut

Last Updated on November 7, 2022

Why You Must Be a Generalist To Manage Your Specialist

Photo by MattSmart

(Cross post from Medium. I’ve been working on this idea for a while. I don’t think it’s quite there yet, but I have decided to publish more work at the early idea stage instead of waiting until it feels fully formed. )

Warren Buffet famously quipped — “don’t ask the barber if you need a haircut.” Buffet explains:

Be careful who you ask for advice, as salespeople’s job is to sell you on what they’re selling. 

I’ve made this mistake many times, asking the salesperson if he thinks what he’s selling is worth it. They’ll always say yes. 

Buffett was alluding to the law of the instrument. 

What is the law of the instrument?

The law of the instrument is a cognitive bias in which people tend to rely too heavily on the same ‘tool’ for every purpose. We have a tendency to rely on the tool that is familiar to us.

This quote which neatly illustrates the law of the instrument is often attributed to Abraham Maslow:

I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail

Why is this interesting?

The law of the instrument extends further into higher risk areas – beyond just the barber or some hammering. It applies broadly when dealing with specialists of any kind. Specialists can include doctors, lawyers, engineers, or anyone giving advice. 

When you’re consulting an expert you might assume that you should take what they say at face value, because they are the knowledgeable one. That is true, but beware the law of the instrument. To put it bluntly:

Don’t ask a surgeon if you need an operation.

Don’t ask a lawyer if you should start litigation.

And at the risk of alienating a chunk of my readers… 

don’t ask a software engineer if you should code it.

They are all going to have a tendency to say YES. 

They are all operating in a narrow sphere of specialization.

We still need specialists, but we need to be careful. While a specialist has specialized knowledge, they bring natural bias towards their own tools.

If you are a strong enough generalist, you can understand and use their advice wisely.

What does it mean to be a generalist?

A generalist is someone who has a wide array of knowledge, on a diverse set of subjects. 

A generalist might not go deep on everything, but they know the basics of a discipline. 

Knowing the basics helps a generalist have more useful interactions with specialists.

A generalist does some basic preparation

A generalist turns up to a conversation with your specialist armed with some basic knowledge. To become a generalist, do some background research yourself, learn enough to be able to at least follow what they are saying. This might be as simple as learning a little lingo.

Before we had the internet, this was difficult. Today you can spend 30 minutes reading online or watching YouTube to get an introduction to a topic. It can be at the most rudimentary level. 

It can seem scary to dive into a discipline that seems complicated and has a lot of jargon, but there are amazing resources online for beginners. 

In my personal life, I often have to consult with doctors and lawyers, and in my professional life, I work closely with software engineers.

Here are five examples from my own experience of managing a specialist — doctors, lawyers, software engineers, architects, and property brokers.


Doctors love to give you medicine! 

I’m not saying you don’t need medicine, I love living in a country with access to the powers of modern western medicine, however a doctor’s whole framing is around treating symptoms with medicine. (And sometimes unfortunately doctors are incentivized to give you medicine, via kickbacks or other incentives).

Become a generalist so you know the right questions to ask.

If you’re consulting your doctor for a diagnosis, a generalist might learn a bit about the diagnosis process before the consultation. Here’s a general diagnosis process, but you could find one relevant to your symptoms.

If you’re getting advice on treatment, a generalist might learn by using the BRAN acronym that Chris Sowers mentioned to me. They might ask their specialist the following questions:

  • What are the Benefits?
  • What are the Risks?
  • What are the Alternatives?
  • What if I/we do Nothing?

(The BRAN acronym is useful in other domains too, maybe your mechanic wants to fix a component of your car or your plumber wants to fix some water leaking in your home.)


Have you ever heard the expression “the lawyers always win”? It means that in a legal battle, the fees are often so hefty that even if you prevail in your lawsuit, the fees you pay to your legal team are so high that you still lose in a different way.

We still have a pretty amazing system with lawyers and courts, however just be aware of their framing and incentives when considering their advice. Litigators will see the opportunity to ligate more clearly than the opportunity for some mediation or walking away.

Become a generalist so you know the right questions to ask. A generalist might learn a little lawyer lingo. Or know the details of the law related to their case, and read about similar cases. 

Here’s an example of a very accessible introduction to US Intellectual Property Law. You can find something related to the area of law relevant to you.

Software engineers

I once heard it called the curse of the programmer in which every problem a programmer encounters in life is is met with a response like “I could write a program to do this”. I can attest to the truth of that having built software myself.

If you are working with a software developer and you don’t have much understanding of what it entails, learn enough to be able to ask the right questions. And learn enough to know if you should even be coding anything. I see this commonly with friends or clients that want to build an app, and want to hire a programmer to build it. I encourage them to become more of a generalist and learn the basics of the product development process first, before consulting a software programmer.

In the product management profession today, we focus on running experiments to test ideas before coding them. Why? Because coding is very costly.

Maybe the no-code tools emerging might help you try out an idea before coding it. A generalist knows what this is before consulting a specialist. Here’s a good no-code primer and here’s a good no-code resource list. 

A generalist knows their options, and knows enough about the software development process to get the most out of their specialist. 


Architects generally want to design beautiful buildings. This might be exactly what you want if you have no price sensitivity. But if you do, then you might want to become a bit of a generalist to manage your architect.

You might want a more practical design. I read this on an architect’s blog “The primary goal of any successful architect …is to absorb the customer’s input and create a living environment that complements and supports their lifestyle.” That sends shivers down my spine! No mention of feasible to build, or fitting within a budget. I want a design that is good value and will actually get completed close to my budget for the project. To achieve that I would need to come to a consultation with that architect with an awareness that their idea of success is different to mine.

I just spent two minutes searching and found a wealth of resources. A generalist might read the basics on how to read plans, or this great post on things to know before a meeting with an architect.

Property brokers

Brokers want to do a transaction with you asap, not wait around until you find the right property for you to buy.

This is an area that’s super important to become a generalist in before taking any advice from the specialist. You can get into real trouble with a property with unexpected problems if it’s your first time working with a property broker and you aren’t enough of a generalist.

Learn the basics of assessing and transacting on property in your location. Here’s a detailed easy to read blog on California residential property.

There are so many other domains where you interact with specialists. The mechanic or other types of brokers come to mind for me. (I could write on this forever but I need to publish this post that I’ve been chipping away at for years.)

Why can’t specialists just be more unbiased? 

You’re probably a specialist in something yourself, so you might have an inkling of how this law affects you. There are a few drivers of the law of the instrument.

The incentives

On one hand it’s their incentives. Of course the lawyer wants to litigate if it’s going to get them a big billable payday. Of course the architect thinks you should redesign your floor plan to modernize it, they get paid regardless of your build costs.

However the law of the instrument is more than just the obvious monetary incentive.

The framing

It’s also the perceptual framing. The old adage is really true, if all you have is a hammer, everything looks like a nail. When you bring a frame to a problem, it’s very difficult to get out of that frame.

The French have a concept called déformation professionelle, which is our tendency to assess situations from the perspective of our profession. Our profession gives us a strong frame that is hard to escape.

Don’t give up on specialists

It’s great to have access to doctors, lawyers, engineers etc, it’s not them in themselves that is the problem. They are important, but you will get a drastically better outcome and avoid problems if you know a little of their discipline.

Maybe it’s most easily remembered with a little latin — caveat emptor —  which means buyer beware.

Become a generalist

The more important, bigger impact situations are the times when you want to become a generalist to manage your specialist. 

Read, listen and watch some content about the specialized area, there is a wealth of information online to support you. Good luck dear generalist! 

Learn about more interesting and useful mental models like the law of the instrument in my newsletter Mental Models Weekly.

General Resources

I’ll list cool resources here, more to come over time.

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