Michael: Okay, Kevin. John Locke's An Essay Concerning Human Understanding. Five words. Go. Kevin: Your brain is an empty notebook. Michael: Nice. Mine is: "Sorry, Plato, you were wrong." Kevin: Ooh, shots fired. I like it. That sets a certain tone. Michael: It absolutely does. We're talking about one of the most foundational texts of modern philosophy, John Locke's An Essay Concerning Human Understanding, specifically Book I, which is his grand assault on a single, powerful idea. Kevin: The idea that we’re born with stuff already in our heads, right? Pre-loaded software. Michael: Exactly. And what’s fascinating, and I think this is the key to understanding him, is that Locke wasn't just some dusty academic in an ivory tower. He was a physician. He was trained to observe, to look for evidence, to diagnose based on symptoms, not on ancient authority. Kevin: Huh. A doctor of the mind, in a way. That actually changes how I think about this. He’s not just philosophizing; he’s approaching the human mind like a body, looking for proof. Michael: Precisely. And in the late 17th century, a time of immense political and religious upheaval in England, this idea of starting from scratch, of building knowledge on the foundation of individual experience, was nothing short of revolutionary. It was a direct challenge to the power structures that relied on people accepting certain "truths" without question. Kevin: Alright, so let's get into it. This "empty notebook" or "blank slate" idea. My gut reaction is to push back. Are you really telling me a newborn baby’s mind is just… static? White noise? Nothing in there at all?

Michael: That’s the million-dollar question, and it’s exactly where Locke starts his demolition project. He challenges what philosophers called "speculative principles"—these supposedly universal, logical truths that everyone is born with. Kevin: Okay, "speculative principles" sounds way too abstract. Give me a concrete example. What are we talking about? Michael: The classic examples are things like, "Whatever is, is," or the big one: "It is impossible for the same thing to be and not to be." The law of non-contradiction. The argument from his opponents, the rationalists, was that these principles are so fundamental, so universally true, that they must be stamped onto our souls from birth. Kevin: I mean, that kind of makes sense. It’s hard to even imagine a world where that isn't true. It feels like the bedrock of reality. How could you not be born knowing that? Michael: Locke’s response is brilliantly simple and, honestly, a little bit savage. He just says: "Go look at a baby." A newborn is crying for milk, it feels warmth, it feels pain. But does it have any concept of "impossibility" or "identity"? Does it lie in its crib pondering the law of non-contradiction? Kevin: Well, no. Obviously not. It’s a baby. It’s busy trying to figure out where its own hands are. Michael: Exactly! Locke’s point is devastatingly effective. He says if these ideas were truly innate, imprinted on every human mind, then children would know them. And so would people he refers to as "idiots," those with severe cognitive impairments. Since they clearly don't, the argument for universal, innate knowledge collapses. The "universal consent" argument is a myth. Kevin: Okay, that’s a powerful point. You can't claim a file is installed on every computer if half the computers can't even open it. But maybe it's just dormant? Maybe it's there, and we just need to "awaken" it with reason when we get older? Michael: He saw that counter-argument coming a mile away. He found it completely absurd. He says that’s like saying all the principles of mathematics are innate, but you only discover them once you learn math. At that point, you’re just learning them! It’s not an act of remembering something you were born with; it’s an act of discovery through experience. Kevin: So the ideas themselves have to be learned first. You can't understand "it's impossible for a tree to be a tree and not a tree at the same time" until you first have the idea of a 'tree' and the idea of 'impossibility'. Michael: You've got it. The building blocks have to come from somewhere, and for Locke, they all come from one of two places: sensation—seeing, hearing, tasting—or reflection, which is the mind observing its own operations. That's it. Everything else is built from that raw material. He uses this wonderful analogy of a sailor. Kevin: I’m listening. I like a good analogy. Michael: He says, "It is very useful for the sailor to know how long his line is, even though it is too short to fathom all the depths of the ocean." Our mind is like that sounding line. We don't need to be born with an innate map of the entire ocean of truth. We just need a reliable tool—our senses and our reason—to measure the depths where we need to navigate, to get us where we need to go safely. Trying to fathom what’s beyond our line is pointless and leads to intellectual shipwrecks. Kevin: That’s a great way to put it. It’s about being practical. We don't need pre-loaded omniscience; we need a functioning toolkit. Alright, I can see how this works for abstract logic. It’s a clean, powerful argument. But this is where it gets tricky for me. What about morality? What about our conscience? A sense of good and evil? Surely that’s built-in.

Michael: And that is exactly where Locke takes his argument next, and where it becomes truly radical and, for many at the time, deeply dangerous. He argues that there are no innate practical, or moral, principles either. Kevin: Whoa. Hold on. So you’re telling me we’re not born with a conscience? That a fundamental sense of right and wrong isn't part of our factory settings? I find that much harder to believe. Michael: Locke would say your difficulty in believing it is proof of how deeply your culture and education have shaped you. He uses the same test: if there were a universal moral law, like "Do not kill," then everyone, everywhere, at all times, would agree on it. And he says, a quick look at history and the world around us proves this is demonstrably false. Kevin: What kind of proof does he offer? Because that’s a huge claim. Michael: He points to some very uncomfortable examples. He talks about armies sacking a town, where soldiers commit the most horrific acts with "calm consciences" because they're operating under a different set of rules. He brings up reports from explorers—and remember, this was the Age of Exploration, so new accounts of different cultures were flooding into Europe—of entire societies where things like infanticide were practiced without any sense of public shame or guilt. Kevin: Wow. That is... that's dark. The idea that a whole society could see leaving a baby to die as normal is profoundly unsettling. Michael: It’s meant to be. It’s a direct assault on the idea of a universal moral compass. His point is that if a principle can be so confidently and serenely broken by entire nations of people, it cannot possibly be an innate law from God stamped on our minds. And this is why his work was so controversial. It was even banned at Oxford a few years after his death. He was seen as undermining the very basis of religion and morality. Kevin: I can see why. If morality is just a local custom, then what’s to stop anyone from doing anything? But he has another example, right? Something about thieves? Michael: Yes, and it’s brilliant. He says, look at a den of thieves or a gang of highwaymen. They break all of society's rules. They lie, they steal, they murder. Yet, within their own group, they often have a very strict code of justice. They have to keep their promises to each other, they have to divide the loot fairly. If they don't, the whole enterprise falls apart. Kevin: Right, there’s no honor among thieves if there’s literally no honor among thieves. Michael: Exactly. And Locke’s insight is that they aren't following this internal code because of some innate principle of 'Justice.' They're doing it out of pure convenience and self-interest. It's a practical rule for survival. He says this shows that what we often call 'justice' or 'fairness' isn't some divine spark, but a set of rules we agree upon for a functioning society. Kevin: So my conscience, the little voice in my head that tells me not to steal the office supplies, isn't an angel on my shoulder? It's just the downloaded software of my upbringing, my parents, my teachers, my society? Michael: According to Locke, yes. He says conscience is nothing more than "our own opinion or judgment of the moral rightness or wrongness of our own actions." And that opinion is formed by our experience. This is why, he argues, people can have such wildly different consciences. One person’s conscience tells them to protest a war, while another’s tells them it's their patriotic duty to fight in it. If conscience were innate, it wouldn't be so contradictory. Kevin: That’s a really challenging thought. It puts a huge amount of responsibility on us. It means we can't just fall back on "I was just following my conscience." We have to ask, "Where did my conscience get its information?" Michael: And that is the absolute core of his entire project. He’s trying to wake people up from their intellectual laziness.

Kevin: So, pulling this all together… Locke smashes the idea of innate knowledge and then smashes the idea of an innate moral compass. It feels like he’s leaving us in a pretty scary place, a world with no built-in truths. Michael: It can feel that way, but I think that’s a misreading of his ultimate goal. He isn't trying to create chaos; he's trying to create empowerment. He's not saying there is no truth or no morality. He's a firm believer in natural law, which can be discovered by reason. What he is saying is that you can't just inherit it. You have to build it yourself. Kevin: So it’s not that the notebook is empty and stays empty. It’s that we are the ones who have to do the writing. Michael: Precisely. And we have to be careful about who we let write in it for us. He has this scathing section at the end where he talks about why the doctrine of innate principles is so popular with people in power. Because if they can convince you that certain principles are innate, they can essentially dictate what those principles are. Kevin: "Principles must not be questioned!" Michael: You got it. That's the quote. It becomes a tool to enforce dogma and stop critical thinking. By arguing for the blank slate, Locke is handing the pen back to the individual. He's saying your mind is your own. Your understanding is built from your experience of the world. Trust that. Use your reason. Don't let anyone, whether it's a king or a priest, tell you that you were born already believing what they want you to believe. Kevin: That reframes the whole thing. The takeaway isn't that nothing is true, but that we have a profound responsibility to figure it out for ourselves, to not just blindly accept what we're told is 'innate' or 'obvious.' Michael: It's a call to intellectual courage. The world is complex, and understanding it is hard work. There are no shortcuts. Kevin: It really makes you wonder, what "innate truths" do we all accept today without questioning them? What are the ideas that are so deeply embedded in our culture that we assume they're just part of human nature? Michael: That is the question Locke leaves us with, and it's as relevant today as it was over 300 years ago. We'd actually love to hear what our listeners think. What's a modern "innate principle" that you think deserves a second look? Let us know. Kevin: A fantastic, and slightly terrifying, thought to end on. Michael: This is Aibrary, signing off.