From Descartes to Destruction: How Radical Skepticism Ate the World

“What can I know for sure?”

René Descartes asked this question in 1641 and soon realized that the answer was vanishingly little. He couldn’t trust the evidence of his sense, since it was entirely possible that everything he saw, heard, smelled, tasted and touched was an illusion—it’s possible he was being deceived by some malevolent force, like Neo in the Matrix. He couldn’t trust his mathematical intuitions either, because for all he knew some malevolent force might be deliberately misleading him whenever he went to carry out a calculation. It seemed all knowledge was doomed—was there anything Descartes could know beyond all doubt?

He had a flash of intuition. He realized that his own process of working through this crisis was… something. Something undeniable.

Descartes was thinking. And if he was thinking, then he must logically exist. He reasoned:

Cogito ergo sum

I think, therefore I am

Descartes knew that he existed. Beyond all doubt. He couldn’t know about anyone else—for all he knew, they could be illusions—but he himself existed.

Descartes went on to ask: if I know that I exist, what else can I know? Well, if I exist, he reasoned, I must have been caused by something. And that thing that caused me must have been greater than myself. Therefore, God exists too.

As you may deduce, this latter reasoning process is full of holes. As Robert G. Brown points out, it relies on several unspoken assumptions, all of which could be false:

  • It assumes temporal persistence (how does Descartes know he wasn’t created moments ago, with false memories?)
  • It assumes causality (why does Descartes need to be caused by anything?)
  • It assumes that everything must be caused by something greater than itself (this one is the most dubious, and we can no doubt think of counter-examples)

It’s difficult to imagine how any further claims can be deduced from Cogito ergo sum without some degree of uncertainty. Are we doomed to know only that we’re thinking, and that we therefore exist?

More worryingly, can we be certain of even that?

In The Watercourse Way, Alan Watts suggests that cogito ergo sum/I think therefore I am might not reveal any deep truth about the universe—only about the structure of Western languages. Western languages—like English, Latin and French (Descartes’ mother tongue)—assume a subject—an agent carrying out the action. Sentences in English must have a subject, even when the action being described might make more sense without a subject—as in the sentence, “it’s raining,” for example (what is the “it” that is raining?). Eastern languages tend not to assume a subject. In Mandarin, for example, you’d just say “Raining.” A Mandarin speaker looking at cogito ergo sum/I think therefore I am might question why, just because a thought is occuring, a subject must exist.

Whatever we think of this argument, it seems to introduce a splinter of doubt into Descartes’ cogito. Fortunately, this sliver isn’t fatal: we can reformulate the cogito as such:

Thinking is happening

Therefore, something is happening

Or, entirely without subjects:

Think

Therefore, am

As a more fully articulated English sentence: I am having a subjective experience, therefore something is happening.

Have we reached the bedrock? Is this the one thing that we can truly know?

Some would argue otherwise. Even this simple logical formulation seems to rely on assumptions:

  • Non-contradiction (how do we know that something and nothing aren’t the same?)
  • The validity of basic logic (if math can be bamboozled, can’t this?)

If this line of argumentation grips you, check out our recent podcast episode on this topic.

Over the past four hundred years, philosophers have tended to focus their attention in the opposite direction: if we can know vanishingly little for certain, then what do we do? How do we live our lives, how do we structure society?

The dominant strategy by philosophers has been to redefine the word “knowledge.” Where Descartes defined knowledge as true things he knew for certain (an infallibilist definition of knowledge), philosophers since have defined knowledge as “justified true belief” or “probable belief” or some other definition where knowledge is held with something less than certainty (a fallibilist definition of knowledge).

Problem is, we don’t have any more of a solid basis for saying that things are probably or justifiably true than in saying that they’re certainly true. Let’s say we assert that statements without contradiction are more likely to be true. How do we justify that statement? It seems true to us, but maybe we’re being misled, and live in a universe riddled with contradiction. Whatever criteria you use to determine which statements are more likely to be true, or more justifiable, those criteria must be based on assumptions, which are justified by more assumptions, back and back and back until you reach a bedrock of unjustified and seemingly arbitrary axioms. We have no better criteria for determining “justified belief” than we do “certain belief.”

So what now? Are we epistemically doomed?

Some philosophers argue that we’ve approached the problem all wrong. To them, trying to take a rational, deductive standpoint was the first mistake: rationality is self-destroying, one moment churning out beautiful structures, and the next consuming them with doubt.

David Hume claimed our knowledge comes not from rationality, but from passion, psychology and practicality. Kierkegaard took this a step further: we can’t reason ourselves to Christianity or atheism, as the rational mind can build or destroy a case for either. Rather, we arrive at our beliefs by taking a leap of faith.

With the demotion of rationality, truth took a blow as well. Philosophers like Nietzsche scorned the search for truth, viewing it as a weak-kneed and sickly distraction from the will to power.

Modern philosophers have reignited the debate. In 2018, Sam Harris and Jordan Peterson engaged in a multi-hour debate on the nature of truth and knowledge, which was viewed by millions of people. The Multiversity recently published a podcast on the topic.

It seems likely that our systems of knowing emerge from some combination of rationality, emotion, and intuition. Perhaps this is how it should be—maybe trying to isolate rationality as the sole pathway to knowledge was always artificial, and doomed to fail. Problem is, if we can’t justify our beliefs with rationality, we’re unlikely to ever arrive at a common, societal-wide belief system. But maybe this is for the best. Maybe a purely rational epistemology is overrated—in any case, it had better be, because it seems to be impossible.

“What can I know for sure?”

René Descartes asked this question in 1641 and soon realized that the answer was vanishingly little. He couldn’t trust the evidence of his sense, since it was entirely possible that everything he saw, heard, smelled, tasted and touched was an illusion—it’s possible he was being deceived by some malevolent force, like Neo in the Matrix. He couldn’t trust his mathematical intuitions either, because for all he knew some malevolent force might be deliberately misleading him whenever he went to carry out a calculation. It seemed all knowledge was doomed—was there anything Descartes could know beyond all doubt?

He had a flash of intuition. He realized that his own process of working through this crisis was… something. Something undeniable.

Descartes was thinking. And if he was thinking, then he must logically exist. He reasoned:

Cogito ergo sum

I think, therefore I am

Descartes knew that he existed. Beyond all doubt. He couldn’t know about anyone else—for all he knew, they could be illusions—but he himself existed.

Descartes went on to ask: if I know that I exist, what else can I know? Well, if I exist, he reasoned, I must have been caused by something. And that thing that caused me must have been greater than myself. Therefore, God exists too.

As you may deduce, this latter reasoning process is full of holes. It relies on several unspoken assumptions, all of which could be false:

  • It assumes temporal persistence (how does Descartes know he wasn’t created moments ago, with false memories?)
  • It assumes causality (why does Descartes need to be caused by anything?)
  • It assumes that everything must be caused by something greater than itself (this one is the most dubious, and we can no doubt think of counter-examples)

It’s difficult to imagine how any further claims can be deduced from Cogito ergo sum without some degree of uncertainty. Are we doomed to know only that we’re thinking, and that we therefore exist?

More worryingly, can we be certain of even that?

In The Watercourse Way, Alan Watts suggests that cogito ergo sum/I think therefore I am might not reveal any deep truth about the universe—only about the structure of Western languages. Western languages—like English, Latin and French (Descartes’ mother tongue)—assume a subject—an agent carrying out the action. Sentences in English must have a subject, even when the action being described might make more sense without a subject—as in the sentence, “it’s raining,” for example (what is the “it” that is raining?). Eastern languages tend not to assume a subject. In Mandarin, for example, you’d just say “Raining.” A Mandarin speaker looking at cogito ergo sum/I think therefore I am might question why, just because a thought is occuring, a subject must exist.

Whatever we think of this argument, it seems to introduce a splinter of doubt into Descartes’ cogito. Fortunately, this sliver isn’t fatal: we can reformulate the cogito as such:

Thinking is happening

Therefore, something is happening

Or, entirely without subjects:

Think

Therefore, am

As a more fully articulated English sentence: I am having a subjective experience, therefore something is happening.

Have we reached the bedrock? Is this the one thing that we can truly know?

Some would argue otherwise. Even this simple logical formulation seems to rely on assumptions:

  • Non-contradiction (how do we know that something and nothing aren’t the same?)
  • The validity of basic logic (if math can be bamboozled, can’t this?)

If this line of argumentation grips you, check out our recent podcast episode on this topic.

Over the past four hundred years, philosophers have tended to focus their attention in the opposite direction: if we can know vanishingly little for certain, then what do we do? How do we live our lives, how do we structure society?

The dominant strategy by philosophers has been to redefine the word “knowledge.” Where Descartes defined knowledge as true things he knew for certain (an infallibilist definition of knowledge), philosophers since have defined knowledge as “justified true belief” or “probable belief” or some other definition where knowledge is held with something less than certainty (a fallibilist definition of knowledge).

Problem is, we don’t have any more of a solid basis for saying that things are probably or justifiably true than in saying that they’re certainly true. Let’s say we assert that statements without contradiction are more likely to be true. How do we justify that statement? It seems true to us, but maybe we’re being misled, and live in a universe riddled with contradiction. Whatever criteria you use to determine which statements are more likely to be true, or more justifiable, those criteria must be based on assumptions, which are justified by more assumptions, back and back and back until you reach a bedrock of unjustified and seemingly arbitrary axioms. We have no better criteria for determining “justified belief” than we do “certain belief.”

So what now? Are we epistemically doomed?

Some philosophers argue that we’ve approached the problem all wrong. To them, trying to take a rational, deductive standpoint was the first mistake: rationality is self-destroying, one moment churning out beautiful structures, and the next consuming them with doubt.

David Hume claimed our knowledge comes not from rationality, but from passion, psychology and practicality. Kierkegaard took this a step further: we can’t reason ourselves to Christianity or atheism, as the rational mind can build or destroy a case for either. Rather, we arrive at our beliefs by taking a leap of faith.

With the demotion of rationality, truth took a blow as well. Philosophers like Nietzsche scorned the search for truth, viewing it as a weak-kneed and sickly distraction from the will to power.

Modern philosophers have reignited the debate. In 2018, Sam Harris and Jordan Peterson engaged in a multi-hour debate on the nature of truth and knowledge, which was viewed by millions of people.

It seems likely that our systems of knowing emerge from some combination of rationality, emotion, and intuition. Perhaps this is how it should be—maybe trying to isolate rationality as the sole pathway to knowledge was always artificial, and doomed to fail. Problem is, if we can’t justify our beliefs with rationality, we’re unlikely to ever arrive at a common, societal-wide belief system. But maybe this is for the best. Maybe a purely rational epistemology is overrated—in any case, it had better be, because it seems to be impossible.