“I dream of a world where the truth is what shapes people’s politics, rather than politics shaping what people think is true,” astrophysicist Neil deGrasse Tyson lamented. Nearly half a century earlier, Hannah Arendt captured the crux of the problem in her incisive reflection on thinking vs. knowing, in which she wrote: “The need of reason is not inspired by the quest for truth but by the quest for meaning.”

This distinction between truth and meaning is vital, especially today, as political propaganda and the “alternative facts” establishment manipulate a public that would rather know than think, preying on the desire for the certitude of ready-made meaning among those unwilling to engage in the work of critical thinking necessary for arriving at truth — truth measured by its correspondence with reality and not by its correspondence with one’s personal agendas, comfort zones, and preexisting beliefs.

This essential discipline of differentiating between truth and certitude is what the influential Austrian-British philosopher Karl Popper (July 28, 1902–September 17, 1994) examined at the end of his long life throughout In Search of a Better World: Lectures and Essays from Thirty Years (public library).

Popper writes:

All things living are in search of a better world. Men, animals, plants, even unicellular organisms are constantly active. They are trying to improve their situation, or at least to avoid its deterioration… Every organism is constantly preoccupied with the task of solving problems. These problems arise from its own assessments of its condition and of its environment; conditions which the organism seeks to improve… We can see that life — even at the level of the unicellular organism — brings something completely new into the world, something that did not previously exist: problems and active attempts to solve them; assessments, values; trial and error.

Popper argues that because the identification of error is so central to the problem-solving process, its corrective — that is, truth — is a core component of our quest for betterment:

The search for truth … no doubt counts among the best and greatest things that life has created in the course of its long search for a better world.

In a sentiment that calls to mind Carl Sagan’s insistence on science’s essential role in democracy, Popper adds:

We have made great mistakes — all living creatures make mistakes. It is indeed impossible to foresee all the unintended consequences of our actions. Here science is our greatest hope: its method is the correction of error.

Looking back on the sometimes troubled but ultimately exponential reach for a better world that had unfolded over the eighty-seven years of his life — “a time of two senseless world wars and of criminal dictatorships” — Popper writes:

In spite of everything, and although we have had so many failures, we, the citizens of the western democracies, live in a social order which is better (because more favourably disposed to reform) and more just than any other in recorded history. Further improvements are of the greatest urgency. (Yet improvements that increase the power of the state often bring about the opposite of what we are seeking.)

What often warps and frustrates our quest for betterment, Popper notes in a 1982 lecture included in the volume, is our failure to distinguish between the search for truth and the assertion of certainty:

Knowledge consists in the search for truth — the search for objectively true, explanatory theories. It is not the search for certainty. To err is human. All human knowledge is fallible and therefore uncertain. It follows that we must distinguish sharply between truth and certainty. That to err is human means not only that we must constantly struggle against error, but also that, even when we have taken the greatest care, we cannot be completely certain that we have not made a mistake… To combat the mistake, the error, means therefore to search for objective truth and to do everything possible to discover and eliminate falsehoods. This is the task of scientific activity. Hence we can say: our aim as scientists is objective truth; more truth, more interesting truth, more intelligible truth. We cannot reasonably aim at certainty. […] Since we can never know anything for sure, it is simply not worth searching for certainty; but it is well worth searching for truth; and we do this chiefly by searching for mistakes, so that we can correct them.

In a sentiment of piercing pertinence today, as a litany of “alternative facts” attempts to gaslight an uncritical public, Popper offers a definition and admonition of elegant acuity:

A theory or a statement is true, if what it says corresponds to reality. [..] Truth and certainty must be sharply distinguished.

Condemning relativistic approaches to truth — ones that regard truth as “what is accepted; or what is put forward by society; or by the majority; or by my interest group; or perhaps by television” — he cautions:

The philosophical relativism that hides behind [Kant’s] “old and famous question” “What is truth?” may open the way to evil things, such as a propaganda of lies inciting men to hatred. […] Relativism … is a betrayal of reason and of humanity.

It is useful here to revisit Arendt’s distinction between truth and meaning, for where truth is absolute — a binary correspondence with reality: a premise either reflects reality or does not — meaning can be relative; it is shaped by one’s subjective interpretation, which is contingent upon beliefs and can be manipulated. Certainty lives in the realm of meaning, not of truth. The very notion of an “alternative fact,” which manipulates certainty at the expense of truth, is therefore the sort of criminal relativism against which Popper so rigorously cautions — something that, as he puts it, “results from mixing-up the notions of truth and certainty.” All propaganda is in the business of manipulating certainty, but it can never manipulate truth. Arendt had articulated this brilliantly a decade earlier in her timely treatise on defactualization in politics: “No matter how large the tissue of falsehood that an experienced liar has to offer, it will never be large enough … to cover the immensity of factuality.”

Popper argues that the ability to discern truth by testing our theories against reality using critical reasoning is a distinctly human faculty — no other animal does this. A generation before him, Bertrand Russell — perhaps the twentieth century’s greatest patron saint of reason — called this ability “the will to doubt” and extolled it as our greatest self-defense against propaganda. The cultural evolution of our species, Popper notes, was propelled by the necessity of honing that ability — we developed a language that contains true and false statements, which gave rise to criticism, which in turn catalyzed a new phase of selection. He writes:

Natural selection is amplified and partially overtaken by critical, cultural selection. The latter permits us a conscious and critical pursuit of our errors: we can consciously find and eradicate our errors, and we can consciously judge one theory as inferior to another… There is no knowledge without rational criticism, criticism in the service of the search for truth.

But this rational criticism, Popper notes, should also be applied to science itself. Cautioning that the antidote to relativism isn’t scientism — a form of certitude equally corrosive to truth — he writes:

Despite my admiration for scientific knowledge, I am not an adherent of scientism. For scientism dogmatically asserts the authority of scientific knowledge; whereas I do not believe in any authority and have always resisted dogmatism; and I continue to resist it, especially in science. I am opposed to the thesis that the scientist must believe in his theory. As far as I am concerned “I do not believe in belief,” as E. M. Forster says; and I especially do not believe in belief in science. I believe at most that belief has a place in ethics, and even here only in a few instances. I believe, for example, that objective truth is a value — that is, an ethical value, perhaps the greatest value there is — and that cruelty is the greatest evil.

Complement this particular portion of the wholly sobering and ennobling In Search of a Better World with Descartes’s twelve timeless tenets of critical thinking, Carl Sagan’s Baloney Detection Kit, and Adrienne Rich on what “truth” really means.