The thirst for knowledge is one of humankind’s noblest appetites. Our desire to sate it, however, sometimes leads us to imbibe falsehoods bottled as truth. The so-called Information Age is too often a Misinformation Age.

There is so much that we don’t know that giving up on experts would be to overreach our own competency. However, not everyone who claims to be an expert is one, so when we are not experts ourselves, we can decide who counts as an expert only with the help of the opinions of other experts. In other words, we have to choose which experts to trust in order to decide which experts to trust.

Jean-Paul Sartre captured the unavoidable responsibility this places on us when he wrote in Existentialism and Humanism (1945): ‘If you seek counsel – from a priest, for example – you have selected that priest; and at bottom you already knew, more or less, what he would advise.’

The pessimistic interpretation of this is that the appeal to expertise is therefore a charade. Psychologists have repeatedly demonstrated the power of motivated thinking and confirmation bias. People cherry-pick the authorities who support what they already believe. If majority opinion is on their side, they will cite the quantity of evidence behind them. If the majority is against them, they will cite the quality of evidence behind them, pointing out that truth is not a democracy. Authorities are not used to guide us towards the truth but to justify what we already believe the truth to be.

If we are sincerely interested in the truth, however, we can use expert opinion more objectively without either giving up our rational autonomy or giving in to our preconceptions. I’ve developed a simple three-step heuristic I’ve dubbed ‘The Triage of Truth’ which can give us a way of deciding whom to listen to about how the world is. The original meaning of triage is to sort according to quality and the term is most familiar today in the medical context of determining the urgency of treatment required. It’s not infallible; it’s not an alternative to thinking for yourself; but it should at least prevent us making some avoidable mistakes. The triage asks three questions:

Are there any experts in this field?

Which kind of expert in this area should I choose?

Which particular expert is worth listening to here?

In many cases there is no simple yes or no answer. Economic forecasting, for example, admits of only very limited mastery. If you are not religious, on the other hand, then no theologian or priest can be an expert on God’s will.

If there is genuine expertise to be had, the second stage is to ask what kind of expert is trustworthy in that domain, to the degree that the domain allows of expertise at all. In health, for example, there are doctors with standard medical training but also herbalists, homeopaths, chiropractors, reiki healers. If we have good reason to dismiss any of these modalities then we can dismiss any particular practitioner without needing to give them a personal assessment.

Once we have decided that there are groups of experts in a domain, the third stage of triage is to ask which particular ones to trust. In some cases, this is easy enough. Any qualified dentist should be good enough, and we might not have the luxury of picking and choosing anyway. When it comes to builders, however, some are clearly more professional than others.

The trickiest situations are where the domain admits significant differences of opinion. In medicine, for example, there is plenty of genuine expertise but the incomplete state of nutritional science, for example, means that we have to take much advice with a pinch of salt, including that on how big this pinch should be.

This triage is an iterative process in which shifts of opinion at one level lead to shifts at others. Our beliefs form complex holistic webs in which parts support each other. For example, we cannot decide in a vacuum whether there is any expertise to be had in any given domain. We will inevitably take into account the views of experts we already trust. Every new judgment feeds back, altering the next one.

Perhaps the most important principle to apply throughout the triage is the 18th-century Scottish philosopher David Hume’s maxim: ‘A wise man … proportions his belief to the evidence.’ Trust in experts always has to be proportionate. If my electrician warns me that touching a wire will electrocute me, I have no reason to doubt her. Any economic forecast, however, should be seen as indicating a probability at best, an educated guest at worst.

Proportionality also means granting only as much authority as is within an expert’s field. When an eminent scientist opines on ethics, for example, she is exceeding her professional scope. The same might be true of a philosopher talking about economics, so be cautious about some of what I have written, too.

This triage gives us a procedure but no algorithm. It does not dispense with the need to make judgments, it simply provides a framework to help us do so. To properly follow Immanuel Kant’s Enlightenment injunction ‘Sapere aude’ (Dare to know), we have to rely on both our own judgment and the judgment of others. We should not confuse thinking for ourselves with thinking by ourselves. Taking expert opinion seriously is not passing the buck. No one can make up your mind for you, unless you make up your mind to let them.