The concept, rooted in philosophical traditions dating back to ancient Greece more than 2,500 years ago, is at the center of a recent discussion published by El País, which examines how ordinary citizens can assess competing claims in an increasingly complex information environment. The article argues that the challenge facing modern societies is not simply the spread of inaccurate information but the ability of individuals to distinguish between evidence-based explanations and narratives that persist despite contradictory facts.
The issue has become particularly visible amid the growing popularity of conspiracy theories and alternative explanations for major events and public policies. According to figures cited from a study by the BBVA Foundation, 22% of people in Spain doubt that humans landed on the Moon, while 28% believe extraterrestrials have visited Earth and that governments are concealing the evidence. Another 5% continue to believe that the Earth is flat.
These findings illustrate a broader phenomenon that extends beyond fringe beliefs. Debates surrounding immigration, climate change, international organizations, and public health have increasingly become fertile ground for claims that challenge established evidence and institutional consensus.
Among the narratives circulating in Spain are assertions that immigration regularization programs automatically grant citizenship, voting rights, or extensive public benefits. Other claims suggest that immigration policies form part of a broader plan known as the “Great Replacement,” a theory alleging the gradual substitution of European populations. Similar allegations have targeted institutions such as the United Nations and policies associated with the 2030 Agenda, with some critics claiming they conceal plans for global political control, the elimination of private property, or increased social surveillance.
Public health has also become a recurring focus of misinformation campaigns. During and after the COVID-19 pandemic, claims emerged alleging that vaccines caused so-called “turbo-cancers,” described as sudden and accelerated tumor growth. Other longstanding allegations have continued to link childhood vaccinations to autism despite extensive scientific scrutiny.
Faced with these competing narratives, the question raised by El País is straightforward: how can non-experts determine what is true?
The answer presented in the article centers on a method that places every claim—including one’s own beliefs—under systematic examination. Rather than accepting statements because they are familiar, emotionally appealing, or widely shared, critical thinking requires testing whether those statements can withstand attempts to disprove them.
This approach differs from simple skepticism or habitual criticism. The article distinguishes between a negative disposition that rejects ideas reflexively and a constructive process that subjects explanations to rigorous evaluation. Within this framework, beliefs remain provisional and open to revision when confronted with stronger evidence.
The intellectual foundations of this approach draw on several influential philosophical traditions. The article references Karl Marx, Friedrich Nietzsche, and Sigmund Freud, often described as thinkers who encouraged suspicion toward appearances and accepted assumptions. It also cites Jacques Derrida’s concept of deconstruction, which involves examining ideas to identify hidden assumptions or overlooked elements in their formation. At the same time, the discussion emphasizes René Descartes’ principle of methodical doubt, arguing that skepticism becomes productive only when applied through a rational and disciplined process.
A central challenge identified in the article is the possibility that individuals may never possess complete information. Human knowledge is inherently limited, leaving open the possibility that new evidence could emerge and challenge existing conclusions. Compounding this difficulty is what psychologists describe as confirmation bias—the tendency to notice and remember information that supports existing beliefs while overlooking contradictory evidence.
To address this problem, the article argues that explanations should be evaluated not by how much supporting evidence they accumulate but by whether they survive repeated attempts at refutation. This principle reflects the philosophy of Karl Popper, whose work emphasized falsifiability as a defining feature of reliable knowledge.
As an example, the article examines a common claim used in debates over immigration: that immigrants take jobs away from native workers. It points to recent data from Spain’s National Statistics Institute and the Foundation for Applied Economic Studies indicating that immigration has had only insignificant effects on employment and wages among native-born Spaniards. It further notes that findings from the Bank of Spain suggest the country’s recent economic growth would have been substantially weaker without the contribution of foreign workers.
The article stresses that such findings should not be accepted unquestioningly simply because they originate from official institutions. Instead, it argues that the burden of proof falls on those advancing alternative explanations. According to this reasoning, individuals challenging established conclusions must present verifiable evidence capable of withstanding independent scrutiny.
This principle also shapes the article’s response to conspiracy theories. It proposes a simple question for those claiming access to hidden truths that contradict widely accepted explanations: if such evidence exists, why has it not been discovered by professionals whose work involves testing and challenging one another’s findings?
The answer frequently offered by conspiracy theorists—that researchers, experts, and institutions are collectively compromised—is presented as a point at which meaningful public verification becomes difficult. The article notes that modern knowledge systems rely on open competition among researchers, journalists, and specialists who seek not only to confirm findings but also to identify errors and contradictions.
The discussion takes on added urgency in the context of artificial intelligence and social media. Algorithms increasingly shape the information people encounter, influencing what stories, opinions, and claims receive attention. According to the article, this environment requires what it describes as a form of “mental fitness,” involving continuous awareness of personal biases and deliberate efforts to evaluate information independently.
Such vigilance includes avoiding judgments based on stereotypes, resisting the tendency to trust only those who share similar views, and remaining willing to reconsider emotionally appealing beliefs when evidence points elsewhere.
The article concludes by linking individual critical thinking to broader social dynamics. Drawing on ideas associated with the Frankfurt School, it argues that public debate should involve examining promises of freedom and progress that have not been fulfilled while remaining committed to evidence-based scrutiny. In an era defined by viral information, algorithmic influence, and competing narratives, the ability to test claims against observable facts remains at the center of how societies evaluate truth.
