The promise of the truth has always been alluring. The most-quoted Gospel verse on evangelical posters and literature is John 14:6, in which Jesus proclaims: “I am the way, the truth and the life.” It resonates because we all have a sense that truth is somehow essential to living well. If your life turns out to have been built on nothing but lies, it is as though it has not been real.

Paris is the capital of France, George Washington was the first president of the United States, water is H 2 O… There are innumerable truths like this, which only idiots or obtuse academics (often thought to be the same thing) would deny.

Somehow, however, the truth has ceased to be plain or simple. Indeed, it is not uncommon to hear people deny that there is any such thing as the truth at all, only opinions: what is “true for you” or “true for me”. The problem is not that we lack a proper understanding of what “truth” means. For practical purposes, it is hard to improve on Aristotle’s early definition: “To say of what is that it is not, or of what is not that it is, is false; while to say of what is that it is, and of what is not that it is not, is true.”

If that sounds obvious, perhaps it’s because there’s nothing mysterious about the ordinary meaning of truth.

Our problem is not primarily with what truth means but how and by whom truth is established. Truth used to seem simple because it was easy to assume that most of what we thought to be true really was true, that things were as they seemed, that the wisdom passed down the generations was timeless.

The world is neither ready nor willing to say goodbye to truth – even in politics

This simplicity has been eroded by a variety of different forces. Science shows us that much of what we think about how the world works is false, and that we are even mistaken about the workings of our own minds. The pace of its development has left us questioning whether today’s orthodoxy will be tomorrow’s outdated fallacy.

The openness of democratic societies has also allowed the free press to expose more and more of what goes on in the corridors of power, making us increasingly aware of the ways in which we are deceived. Truth has become much less plain and simple, but I see no evidence that most people have ceased to believe in it. People remain as outraged by lies as they ever have done.

That’s why talk of a “post-truth” society is misguided. We wouldn’t even be talking about post-truth if we didn’t think truth mattered. The world is neither ready nor willing to say goodbye to truth, even in politics, where it sometimes seems as though it has already taken its leave.

The antidote is not a return to the comfort of simple truths.

To rebuild belief in the power and value of truth, we can’t dodge its complexity. Truths can be and often are difficult to understand, discover, explain, verify. They are also disturbingly easy to hide, distort, abuse or twist. Often we cannot claim with any certainty to know the truth. We need to take stock of the various kinds of real and supposed truths out there and understand how to test their authenticity.

History and philosophy can be our guides, the former enabling us to see how the idea of truth has actually been used and abused, the latter helping us to see how it should ideally be. They can also show us that with honest intent and clarity of mind, we can guard against such misuse and see that the claim that we live in a post-truth world is the most pernicious untruth of them all. It serves the interests of those who have the most to fear from the truth, plain and simple or not.

A Short History of Truth by Julian Baggini is published by Quercus on 21 September, £9.99. Order it for £7.49 at bookshop.theguardian.com