The Reach of Reason: On the Belief That We Can Understand

Recovered still, Source SIGNAL 06-2025, integrity 85%.

SIGNAL 06-2025 // Fragment: The Reach of Reason: On the Belief That We Can Understand

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Recovered From: /ghost_archive_2025/
Declassification Date: 2025-09-11

I. The Question - What Can I Know?

We don’t ask what we can know when things are going well. We ask it when something breaks. When we realise we were wrong about someone. When we feel certain of something, and then watch that certainty dissolve. When we trust what we’ve been told, only to find out it was never true. The question shows up in moments of personal collapse, when belief becomes fragile. And once it’s there, it’s hard to ignore.

What can I actually trust? What do I really know? And how do I know it?

This is not a purely academic question. It touches relationships, politics, science, memory, self-perception. We form opinions, make decisions, take positions. But on what basis? When we begin to seriously examine our knowledge, we often find that much of it rests on shaky ground: assumptions, habits, social norms, or ideas we’ve inherited without question.

Philosophy has long returned to this problem: what counts as knowledge, and how we respond when certainty fails. Some thinkers search for foundations. Others argue that searching for perfect certainty is what leads us astray in the first place. Still others focus what it means to live and make sense of the world from a particular position, with limited information and real consequences.

In this essay, we’ll look at how René Descartes, Sextus Empiricus, and Simone de Beauvoir each approached the question of knowledge. Their answers don’t overlap. In fact, they sometimes contradict. But each one takes seriously the experience of uncertainty and tries to offer a different way of living with it.

II. The Historic Spark - Three Thinkers Confront the Edge of Knowing

The question of what it means to hold a belief and call it true has shaped entire traditions of philosophy. For some, the goal is to find certainty. For others, it's about learning to live with doubt. In this essay, we’ll look at three philosophers who approach this issue from very different directions, shaped by the intellectual and existential problems of their time.

René Descartes lived in 17th-century Europe, during a time of scientific revolution and religious upheaval. Faced with the breakdown of inherited systems of belief, he searched for an indubitable foundation. A belief that could not be doubted, even under the harshest scrutiny. He is often credited with launching modern philosophy through his method of radical doubt.

Sextus Empiricus, writing in the Roman Empire around the 2nd century CE, belonged to the Pyrrhonian skeptical tradition. He did not seek unshakable knowledge, but questioned the need for it. For Sextus, the goal of inquiry was not certainty but peace of mind, which he believed could only come from suspending judgment and letting go of the demand for final answers.

Simone de Beauvoir, writing in the mid-20th century, approached knowledge not as an abstract puzzle, but as something tied to experience, embodiment, and responsibility. Influenced by both phenomenology and existentialism, she explored how people navigate ambiguity, and how knowledge is shaped by perspective, history, and power.

These three thinkers represent different intellectual traditions: rationalism, skepticism, and existentialism; but all return to the same tension: how can we trust what we believe to be true? And what happens when that trust falters?^[1]

III.1 – René Descartes: Certainty from Doubt

René Descartes was born in 1596 in La Haye, France. A time when Europe was caught between worlds. The authority of the Church was declining. The scientific method was beginning to reshape how people thought about nature, medicine, and astronomy. Long-standing truths were being overturned, and with them, a deep anxiety about what could still be trusted.

Descartes was educated in the Jesuit tradition, steeped in Aristotelian logic and classical theology. But he found that the ideas he was taught were often built on weak foundations. Different systems of thought contradicted one another, and most relied on assumptions inherited rather than proven. In a world of collapsing certainty, Descartes wanted to start again.

This led him to develop what has become one of the most well-known methods in Western philosophy: radical doubt. In Meditations on First Philosophy^[2] he describes a process of stripping away every belief he had ever held, testing each one to see if there was any possibility it could be false..

He questioned not only his senses (which can deceive), but even mathematics (which could be manipulated by an evil demon). He questioned the reality of the external world, of the body, of memory. Everything fell away, except one fact he could not escape:

“I think, therefore I am.” ^[3]

This became Descartes’ foundational certainty. Even if everything else is an illusion, the very act of doubting confirms that there is a mind doing the doubting. He exists even if everything else is in question.

From this foundation, Descartes rebuilt knowledge. He used rational argument to establish the existence of God, the reliability of clear and distinct ideas, and eventually the existence of the physical world. But the key was this: he did not accept anything as true until he had tested it against the possibility of doubt.

Descartes is classified as a rationalist: someone who believes that true knowledge comes not from the senses, but from reason. His philosophy launched a new trajectory in epistemology, and influenced fields from mathematics to psychology. But his work also created sharp divisions. Later philosophers would critique his dualism as well as his dependence on God as a guarantor of truth.

III.2 – Sextus Empiricus: The Peace Found in Suspension

Sextus Empiricus lived during the 2nd or early 3rd century CE, likely somewhere within the Roman Empire. His precise biography is uncertain. What we do know is that he was a physician, trained in the Empiricist school of medicine, and a philosopher associated with Pyrrhonian skepticism, one of the most radical traditions of thought to survive from antiquity.

Unlike Descartes, who sought an unshakeable foundation for knowledge, Sextus questioned whether such a foundation was necessary, or even possible. Drawing on the legacy of Pyrrho of Elis (4th century BCE), he argued that human beings are trapped in a cycle of dogmatism: we form opinions, defend them, and suffer when they fail. The problem, he said, is not just the content of our beliefs, but the need to hold beliefs as if they were absolutely true.

Sextus did not call for disbelief, nor did he claim to know that nothing could be known. Instead, he introduced a third path: suspension of judgment. His central work, Outlines of Pyrrhonism, is not a manifesto but a manual. It presents philosophical arguments not to prove anything, but to balance every claim with an equal and opposite counter-claim, until the reader begins to see how fragile certainty can be.

“The Skeptic does not dogmatically insist upon the inapprehensibility of things… but says that, owing to the equipollence of the objects and reasons opposed to each other, we are not able to decide the matter and must suspend judgment.” ^[4]

For Sextus, this suspension leads to ataraxia (a state of tranquility). Without the pressure to be right, or the fear of being wrong, one becomes free from the emotional turmoil that comes with dogmatic belief^[5]. This was not an intellectual trick. It was a practical method for living in a world of uncertainty.

Importantly, Sextus distinguished between everyday life and philosophical inquiry. In daily affairs, the skeptic still eats, speaks, and participates in society. What they avoid is ascent to truth-claims about the ultimate nature of reality. As he put it:

“Skeptics follow appearances, but without holding beliefs.” ^[6]

Philosophically, Sextus represents epistemological humility in its purest form. He does not say what is. He does not say what isn’t. He simply withholds judgment, recognising that for every argument, another can be raised. In this way, he sees knowledge not as a fixed possession, but as a balance that can never fully settle.

His influence on later thought is hard to overstate. Sextus’ works were rediscovered during the Renaissance and deeply shaped early modern philosophers, including Montaigne, Hume, and even Descartes. Whose radical doubt echoes Pyrrhonian method, though Descartes quickly diverged in seeking certainty where Sextus found peace in its absence.

In the context of the question What can I know?, Sextus answers: perhaps nothing with certainty, but that need not disturb you. His skepticism is not paralysis. It is a way of navigating the world without being captured by it, of thinking deeply without being trapped by the need to conclude.

III.3 – Simone de Beauvoir: Ambiguity and Situated Knowledge

Simone de Beauvoir was born in Paris in 1908 and came of age in the aftermath of the First World War, a time when belief in reason, progress, and Western certainty had begun to falter. She was part of a generation that witnessed both world wars, the rise and collapse of fascism, and the brutal legacies of colonialism. For her, the question of knowledge was not just philosophical. It was intimately political, personal, and historical.

Beauvoir studied philosophy at the Sorbonne and became a leading figure in existentialist thought, alongside Jean-Paul Sartre. But her work extended well beyond traditional academic boundaries. She wrote novels, memoirs, and deeply personal philosophical texts.

Where Descartes sought clarity through method, and Sextus suspended belief to preserve inner peace, Beauvoir focused on what it means to live as a thinking subject in a world that resists simple categories. She understood that knowledge is never neutral. It is shaped by the perspective of gender, class, history, and relationship to power.

In The Ethics of Ambiguity ^[7] Beauvoir argued that human beings are both subjects and objects: we are free consciousness, capable of reflection and meaning-making, but we are also bodies in the world, bound by circumstance. We are never fully detached observers, nor are we purely determined. We live in ambiguity.

“Man is free; but he finds his law in his very freedom.” ^[8]

Beauvoir rejected the idea that knowledge requires detachment. Instead, she insisted that understanding must begin from the fact that we are embedded in time, culture, and physical form. For her, there is no “view from nowhere.” Every claim to knowledge must be understood in light of who is making it.

This does not mean all knowledge is invalid or relative. But it does mean that certainty must always be held with humility, because every knower is partial. She wrote:

“To will oneself moral and to will oneself free are one and the same decision.” ^[9]

For Beauvoir, the pursuit of knowledge is never isolated from the pursuit of freedom. We are responsible not only for what we know, but for how we know, and how that knowledge affects others. This is especially evident in her feminist work, where she critiques how male philosophers historically treated women not as subjects, but as objects.

Philosophically, Beauvoir is often associated with existentialism, phenomenology, and feminist epistemology. But she resists simple labels. Her legacy lies in insisting that truth must take account of the knower. And that to ask what can I know? is also to ask who am I, here and now, trying to know?

IV. Tensions and Echoes – How We Live with Uncertainty

Each of these thinkers: Descartes, Sextus, and Beauvoir, confronts the fragility of knowledge. But they do not answer it with the same tone, nor from the same place. Their philosophies grow from different pressures: Descartes seeks structure in the collapse of old authorities, Sextus resists the suffering born from clinging to opinions, and Beauvoir engages the tension between freedom and situatedness in a world shaped by history and embodiment.

Descartes and Sextus: Doubt with Opposite Intentions

Descartes begins with doubt in order to escape it. His is a method of a systematic unravelling designed to reveal something certain at its core. Doubt, for him, is a tool. Once he finds the foundation he begins to rebuild. His confidence grows as he moves outward from the self.

Sextus, by contrast, doubts in order to stay in uncertainty. He offers no reconstruction, no foundational belief. His goal is not to build knowledge, but to let go of the need for it. If Descartes seeks truth through clarity, Sextus seeks peace through balance. He doesn’t solve doubt, but he makes room for it to breathe.

Beauvoir and Descartes: Freedom from Very Different Foundations

At first glance, Beauvoir seems far from Descartes. He locates certainty in abstract thought. She grounds it in lived, embodied existence. He isolates the self from the world to find clarity. She insists that the self is always already in the world, and that clarity requires engaging with its ambiguities.

And yet, both believe in human freedom, and both believe that how we know matters. Descartes trusts reason as a universal tool, available to all minds equally. Beauvoir sees reason as historically shaped, filtered through bodies, relationships, and power structures. She doesn’t reject reason, but she refuses to pretend it is untouched by life^[10].

Sextus and Beauvoir: Holding Belief Lightly, Living Fully

While their traditions are far apart, Sextus and Beauvoir share a certain caution: they both reject the rush to final answers. Sextus suspends judgment to find peace. Beauvoir embraces ambiguity to preserve integrity. Neither can accept dogma, though Beauvoir resists the ethical consequences of disengagement.

Where Sextus offers tranquility through detachment, Beauvoir pushes back: some beliefs matter. They shape how we treat others, how we act, how we respond to oppression or injustice. For her, living in ambiguity means walking forward without guarantees, but with attention.

V. Return to the Question – Living with the Unknown

What can I know? It’s not a question that ends. It shifts shape. It moves between crisis and curiosity. Sometimes it arrives as doubt, sometimes as disillusionment, sometimes as a quiet pause when certainty fails to hold. We rarely ask it in moments of comfort. It tends to emerge when something essential has slipped. When belief becomes unstable, when trust has been shaken, when we no longer know what to believe.

Descartes wanted firm ground and tried to rebuild the world from a single undeniable truth. Sextus stepped away from the whole pursuit, letting go of the need to hold beliefs at all. Beauvoir leaned into ambiguity, insisting that what we know depends on where, and who, we are.

They do not answer the question the same way. If we’re looking for a clear conclusion, it will not come here. These essays are not for that. They are for marking the questions that never fully leave us, and showing that others, centuries ago, across cultures and systems, have wrestled with the same weight.

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