Democracy is a pretty good way to run a government. Sure, it's not perfect, and perhaps rule by Philosopher Kings and Queens would be better (for philosophers at least), but the fact that people who don't have democracy agitate, protest, and fight for it shows that it remains a highly desirable way of governing.
(Quick aside - I'd be happy to volunteer my services as Philosopher King should anyone require it.)
This idea is best summed up in Winston Churchill's famous quip that democracy is the worst form of government except for all the others we've tried. Democracy, viewed this way, is the least bad option for ruling.
But what is about democracy that makes it good - or less bad than the others?
Over the last 2500 years, philosophers and political theorists have put forward a lot of explanations to try and answer this question. One is that democracy is good because it is one of the few systems of government to rely on consent. Societies need rules to properly function and often, people disagree with particular rules.
But if everyone gets a say in the creation of these rules, then at least we've agreed to play by the rules, even if we disagree with them.
A similar explanation is based on equality and egalitarianism. We would all prefer to be the boss - benevolent dictators shaping the world as we see best.
Unfortunately (or perhaps fortunately), we can't all be dictators. In fact, the only system of government that rational dictators with equal power would agree to is to no more than an equal say for everyone else. So rational egoism makes us accept equality amongst our fellow citizens - one vote, one value.
Perhaps the most powerful justification of democracy though, is epistemic - that democracies tend to make better choices than other forms of government. This is most famously articulated in what's known as Condorcet's Jury Theorem and sometimes called the Wisdom of the Crowds.
Democracy's epistemic superpower
CJT is a mathematical proof that shows that people who on average each have a better than even chance of being correct in a decision increase the chance of a correct majority decision when deciding as a group. The chance that the majority vote is correct increases as the number of voters increases.
To add some real figures, it means that if only 1000 people, each of whom on average have just a 51% chance of being right on some issue, then a majority vote of the group will have 99.999% certainty of being right.
That. Is. Amazing.
Democracy has the power to turn the knowledge of a group of 'average' people into something better than an expert!
Of course, there are some important assumptions behind that result. One is that we are asking the right questions. CJT only works if we are asking questions that can be answered correct (as opposed to questions about competing values which may or may not have a 'right' answer).
The key assumption however, is that the chance of each voter being correct is independent of whether other voters are correct.
No-one reasons perfectly and we all make mistakes. But if the errors in our reasoning are different (or more accurately "statistically independent") then these reasoning errors will cancel each other out when we reason as a group.
So if we are trying to estimate the weight of a cow at a fair, or how many jelly beans are in a jar, then some of us might overestimate and some of us might underestimate, while most of us will be wildly incorrect.
Yet when we aggregate the results of everyone and average them out, these over- and underestimates balance out and the collective result of a group of 'just better than average' people will far exceed the results of individual experts.
But if the reasoning errors of individuals are systematic rather than independent, we have a problem. If we all have a tendency to underestimate the number of jelly beans in the jar (or overestimate the success of some economic policy) then the group decision will be much worse than both the individual expert and even the average voter.
CJT is symmetric - it works in both directions. If those 1000 voters are only 49% likely to be right on average, then the majority vote will be 99.999% likely to be wrong.
Systematic bias turns democracy's epistemic superpower into an idiocracy.
Critical thinking to the rescue
Humans have amazing cognitive abilities. We can compose concertos, paint works of art, and decipher complex languages. We can identify patterns in ambiguous data with amazing ease - faster and more accurately than even the best AI running on super-computers.
We can beat the processing power of super-computers because we take cognitive shortcuts in many circumstances - rules of thumbs for decision making psychologists call heuristics.
But these same cognitive shortcuts also lead us to make errors when they are used in inappropriate settings. We overly discount distant outcomes, we assume events will be more like the near past rather than average past, and we substitute difficult problems for easy ones.
Importantly, these errors are systematic. People consistently repeat the same types of errors across a wide range of situations. This is what psychologists mean when they talk about cognitive biases.
Thankfully we can reduce or overcome these systematic biases through critical thinking. An explicit focus on thinking skills and metacognition in formal education and beyond can make us aware of our cognitive biases, reduce them, and improve our logical reasoning.
Critical thinking can also help us ask better questions in the first place. Critical thinking helps us uncover our assumptions and reframe issues in ways that can take advantage of democracy's epistemic superpower.
This is why democracy requires critical thinkers. Critical thinking can help us overcome systematic biases in our reasoning by teaching us to make our own thinking the object of our analysis.
We'll never be perfect reasoners. But by learning to think critically, we can reduce or eliminate the systemic biases in our thinking processes. Then, democracy's epistemic superpower can do the rest.