Philosophy is no more or less than the search for wisdom. It deals with all manner of problems which everyone faces in their lives, and by thought and logic attempts to solve them. Since we live in a terrifically complex universe lots of philosophy is itself, very complex. Modern academic philosophy can be almost impenetrable to an outsider, and anything not couched in the terms of the academic philosopher is considered simple musing. However, philosophy has thankfully provided lots of short, pithy philosophical statements to ponder. Here are ten of the best one-liners drawn from Western philosophy.

You cannot step in the same river twice.

Heraclitus of Ephesus, also known as the Weeping Philosopher and Heraclitus the Obscure, has left us only a few philosophical sentences. Due to this lack of original writing, Heraclitus’ philosophy remains hard to characterize. His belief seems to have been that the universe is in a constant state of flux, as this famous quote indicates. By the time that you attempt to step into the river a second time, the waters of the river will have moved on and so, the river will not be the same one you stepped into the first time. The sentence also has a second meaning; you cannot step into the same river again because you are no longer the same as the person who took the first step. The question of how identity is preserved over time is one which still animates philosophers today.

Death need not concern us because when we exist death does not, and when death exists we do not.

Epicurus and Epicureanism, has suffered for many years from a misapprehension about what his philosophy teaches. Epicureanism is a hedonistic philosophy in that it teaches that pleasure is to be sought, but only to the extent that pleasure is the freedom from pain and fear. Epicurus also taught on the gods and death. Epicurus is famous today for his questions regarding the problem of evil existing if there are gods and for this statement about death. Because death, being dead rather than dying, involves no pain, for Epicurus the state of death is a good thing (or at least not to be feared). Epicurus is well beloved of atheists and humanists today because of his rational outlook. In the Roman period, tombs of Epicureans would have this carved on their tombs- I was not. I was. I am not. I do not care.

God is dead.

Poor Friedrich Nietzsche has suffered from misconceptions quite as much as Epicurus. After his death, Nietzsche’s sister took control of his writings and edited them to fit in with Nazi ideology. This association with the Nazis – which was no fault of his own – has harmed his reputation ever since. This three word aphorism is perhaps Nietzsche’s most famous. It should not be taken to mean that God is literally dead, for Nietzsche does not believe God ever existed. As with many short sentences, this one can bear many contradicting interpretations. Nietzsche suggests that it is the inability of humans to live up to a moral code which has destroyed God, but it is equally possible to see it as a statement that God has no place in the modern world.

Man is the measure of all things.

This is the most famous saying of Protagoras, though it is in fact, only the first portion of his statement. The full line runs ‘Man is the measure of all things; of things that are that they are, and of things that are not that they are not.’ Protagoras’ relativism is one of the most extreme ever argued. This means that truth is relative and for each individual truth is different. This can be true with things like temperature – you might find the evening chilly, but for me it is warm. However, we can all agree on the absolute temperature in degrees. Protagoras would disagree and would say that all of our knowledge is sense based and therefore unique to each individual. The problem with relativism is that it makes philosophical discussion impossible; what you think you say and what I hear might be completely different, if we are unable to agree on objective truth.

A categorical imperative would be one which represented an action as objectively necessary in itself, without reference to any other purpose.

Kant is one of the giants of Western philosophy. Someone once said that philosophers who came before Kant had the enormous benefit of never having to study Kant. It is true that Kant’s philosophy can be heavy going to read and understand, but his theory of the categorical imperative is one deserving study. A categorical imperative would be something like ‘It is never right to lie.’ The test of the categorical imperative is whether it should be universally used. So, if lying became universal then trust would be abolished, therefore lying is wrong in all cases. Whether you agree with categorical imperatives or not, and situational ethics is the flavor of the modern age, we must all consider why things may or may not be good.

Man is born free and is everywhere in chains.

The concept of the social contract did not originate with Rousseau, but he was the great popularizer of the concept so neatly summed up in this aphorism. Hobbes thought that in the state of nature, man’s life was one of terrible beastliness (nasty, brutish and short). The social contract is the giving up of these natural freedoms by an individual to better accomplish his goals by working within society. Since man is born free, the chains we wear are ones we choose to wear. It is for the individual to decide which freedoms are worth giving up.

The unexamined life is not worth living.

For me this statement of Socrates’, as told by Plato, is sufficient to explain the necessity of studying philosophy. Everyone is pitched into the world blindly and makes do as best they can with the things they are given. For many, this muddling through is hard enough, and examining their motives and the rightness of their actions is just an added, and superfluous, difficulty. However, if we do not examine our lives and use the wisdom we gain from it to plan the future, we are no better than animals following instinct to survive. To take control of your life you must engage your mind. This is not to say that everyone must become a new Socrates, or study academic philosophy, but to paraphrase Voltaire ‘we must all cultivate our own wisdom.’

I think therefore I am.

Je pense donc je suis. Cogito ergo sum. These are the words which Descartes used to slay total nihilism. Nihilism is the philosophical denial of existence, either of anything at all or more specific portions of existence. Everyone, at some point in their philosophical musings, wonders whether anything at all exists. Descartes was clever enough to see that pondering, doubting, existence was sufficient to prove that at least one thing exists; the thinker. This has given philosophy something to build on as we can now be certain that one thing exists. There have been criticisms of Descartes argument as a tautology (I think therefore I am) but the basic principle stands as a buttress against the void of nihilism.

The writer Milan Kundera has joked “‘I think, therefore I am’ is the statement of an intellectual who underrates toothaches.”

Entities should not be multiplied unnecessarily.

William of Ockham was a noted English logician of the 14th century. Ockham’s razor is often quoted simply as ‘the simplest explanation is usually the right one.’ This is a gross simplification of a powerful logical tool. A better stating of it would be something like ‘All things being equal, the simplest explanation is more often correct.’ We live in a complex world where the answer to any question is often very complex. All things being equal, with no more evidence for one solution than another, we should not posit the existence of an agent we do not need to explain a phenomenon. When thinking about a subject, we should use the simplest reasoning possible unless the evidence compels us to include an extra agency.

There has been a recent innovation in the world of philosophy which claims to put Ockham’s razor to rest. Scientists are notoriously sniffy of philosophy, and so Mike Alder has created an improvement of Ockham’s razor – Newton’s Flaming Laser Sword. Simply put, this new philosophical tool states ‘That which cannot be settled by experiment is not worth debating.’ The Flaming Laser Sword certainly simplifies things; one thinks Ockham may have approved of it.

Do unto others as you would have them do unto you.

This is called the Golden Rule of ethics and has been stated by many people in many places at many times, and so no one religion or philosophy can lay claim to it. This maxim deserves the top spot on any philosophical one-liner list because it so neatly sums up a system of ethics by which many people live their lives. The statement is a challenge as well as an instruction – we must try to empathize with others to understand how we ourselves would wish to be treated if in the other person’s place. There may be exceptions to the rule and it may not be sufficient to a complete moral doctrine, but as a simple rule for daily life it is hard to think of something which would so improve everyone’s lives if put universally into effect.

There is nothing so absurd but some philosopher has said it.

I know philosophy leaves some people cold, so here is a quote from Cicero. Cicero translated Greek philosophy for a Latin audience so he surely knew what he was talking about. I hope this list has gone someway to showing that not all philosophy is bunk, however.

When it came out in 1999, The Matrix was a film for the record books. With incredible performances from actors Keanu Reeves and Laurence Fishbourne, cutting-edge special effects, unbelievable action scenes, and an undeniably good soundtrack, The Matrix quickly took the world by storm. But lurking beneath the surface of these praiseworthy aspects of the film is the fact that the plot is downright twisted. It weaves a narrative of confusion, one that makes you question your own reality, as it mesmerizes you with its aesthetic beauty.

Millions of people walked out of the movie theaters in 1999 wondering if the world they were living in was truly the real world. And all of this comes from some deep philosophical questions that brilliant people have been pondering for thousands of years. But what if all of the mind-boggling concepts were nothing new? It turns out The Matrix used a lot of ideas from philosophers, both modern and ancient.

Here are 10 philosophical ideas The Matrix used…borrowed…stole (you pick) from other people.

Related: Top 10 Unexpected Future Applications Of Quantum Computers

10 Cartesian Dualism

Cartesian dualism is a philosophical theory in which the universe is divided into two equal and opposite types of existence, called “mind” and “matter.” Developed by French philosopher Rene Descartes, it’s a direct extension of his philosophy of mind-body dualism. Descartes was obsessed with the point where the body ends and the mind beings.

The question at hand is whether the mind is an abstraction that exists in the physical universe or whether the physical universe is an abstraction that exists in the mind. And, using my mind, the only thing I can ever truly prove is the mental world of my thinking.

This problem was the cornerstone of the movie, The Matrix.

There was a “real” world, and then there was the abstraction that existed only in the mind. The real world existed, but what the characters experienced was a carefully curated artificial simulation that existed only in their minds—until they went down the rabbit hole.

Where do the body end and the mind begin? And how can we truly know if we can only think with our minds, and thus, we can only say for certain that our minds exist?^[1]

9 Plato’s “Allegory of the Cave”

Plato’s “Allegory of the Cave” comes from his work The Republic. It starts off with a conversation between Socrates and Glaucon where they discuss the idea of how we see the world. How do we know if the reality we’re experiencing is actually real? Can we use our senses?

Socrates didn’t think so, and he asks us to imagine a cave with people in it who’ve never been outside of it. There’s a fire in the front and a blank wall in the back. On the back wall, shadows are cast using the light from the fire, showing the activity happening outside the cave—but only in shadow.

The people in the cave can only see what is in front of them, and they can only hear the noises of other people. They’re cut off from the world outside the cave and chained to the wall inside the cave.

Considering these people have spent their entire lives in the cave, they have no clue there’s a real world outside of the cave, one that’s totally different from the mirage they’d always known.

This begs the question, how do we know that what we experience isn’t just shadows, like “the woman in the red dress?” How do we know if we’ve never stepped outside of our own “caves” and into the “real” world that creates them?^[2]

8 Nick Bostrom’s Simulation Hypothesis

The Simulation Hypothesis, proposed by Swedish philosopher Nick Bostrom, argues that it’s possible that we are living in a computer-simulated world created by an advanced civilization, possibly from the future. Bostrom bases this hypothesis on three criteria: the mathematical odds of the existence of the simulated world, the technological feasibility of running a simulated world, and the “intelligence explosion” required to create that simulated world. More on this later…

In the simulation theory, the people in the simulated world are unaware that they are living in a simulation.

Bostrom demonstrates that it’s more likely that we’re living in a simulated world than a real one right now. One real-world could create as many simulated worlds as it wanted to, as long as it had the technological power to do so, so the odds stack up in favor of this world being simulated.

The implications of this are stunning. The Matrix borrowed heavily from the Simulation Hypothesis when it created its own simulated world. So, how do you know that your entire life isn’t just a computer simulation?^[3]

7 Berkeley’s Immaterialism

There is a school of thought called immaterialism, which was conceived by the Irish philosopher George Berkeley. Immaterialism is the idea that physical objects do not exist in a world of their own but rather form a part of a larger whole in a world consisting only of intangible things. For Berkeley, the world doesn’t exist independently of the mind. There is only the mind, and the mind invents the experiences we call the world.

In The Matrix, the computer programmed the characters’ minds, but their minds created their experiences—experiences that weren’t real.

Berkeley asks us how we can truly know if what we’re experiencing is the real thing or just our imaginations.

Remember that scene where they were eating amorphous muck out of bowls and missing fat, juicy steaks? How do you know that every steak you’ve ever eaten wasn’t really just a blob of muck that your brain interpreted as steak?^[4]

6 Gilbert Harman’s Brain in a Vat

In a thought experiment by philosopher Gilbert Harman, a scientist places a conscious brain in a vat of nutrients and water and makes him believe that he is a brain in a vat. The scientist then stimulates the vat with electricity and monitors the changes in the person’s mental state. Unbeknownst to the person, the scientist’s intentions are not to study the brain but rather to test the question, “What is it like to be a brain in a vat?”

In one experiment, the scientist stimulates the vat with electricity, and the person feels pain. In another experiment, the scientist stimulates the vat with electricity, and the person feels nothing. In yet another, the scientist stimulates the vat with electricity, and the person feels a sense of freedom. In a final test, the scientist stimulates the vat with electricity, and the person feels a sense of confidence.

The parallels should be obvious. From downloading Kung-Fu moves to the “woman in the red dress,” The Matrix was controlling the characters’ minds in a giant vat farm.^[5]

5 The Experience Machine

The philosopher Robert Nozick wrote a short thought experiment called “The Experience Machine.” In it, an individual wakes up in a laboratory designed to simulate whatever life they can imagine. The individual then realizes that they have been plugged into this machine. The individual must decide whether to stay in the machine’s simulation or wake up.

This makes us ask ourselves, can we find happiness living a simulated life?

The individual in the experiment is faced with choosing to stay in the machine or wake up. They can wake up, but only if the machine is destroyed. If they choose to stay in the machine, they will find happiness in the life they are living but will never know what it is like to wake up.^[6]

So, if you were Neo, would you take the red pill or the blue pill?

4 The Constructivism of Jean Piaget

Constructivism is a theory of knowledge that says that knowledge is constructed by the individual’s interactions with the world. Knowledge is made up of meanings, which are created by the individual. The individual then assigns meaning to an object or experience that is not already known. The individual then shares this meaning with others. This creates a social phenomenon constructed by the individual’s interactions with the world.

Constructivism plays a crucial role when Neo joins the rest, and they must learn completely new realities. The laws of physics are totally different in the real world than they were in the simulated world, and the team needs to develop a theory of knowledge together that’s consistent with the real world in order to overcome the Agents.^[7]

3 Kant’s Theory of Freedom

German Philosopher Immanuel Kant once said, “You must be free in order to make yourself into what you are capable of being.” He believed that moral law was to know thyself as a free person. For Kant, freedom is a necessary component of happiness, and happiness without freedom is impossible. If happiness was a gift that was given to you by an outside force, it wouldn’t be true happiness.

And The Matrix played heavily on this concept when it forced us to ask whether we’d prefer to live a happy lie or an uncomfortable truth. When plugged into the machine, the people are happy living in the artificial “caves” of their own minds. The machines created a simulation that allowed the characters to be happy—but only at the expense of freedom.

So what’s more important to you, happiness or freedom?

The people living in The Matrix were happy, but they weren’t free.^[8]

2 Nick Bostrom’s Superintelligence

Bostrom’s work discusses the possibility of an artificial intelligence “breakthrough” that would lead to an intelligence explosion. This would result in the creation of intelligence so powerful that it would be able to control the entire world. The intelligence would be so powerful that it would be able to build an even more intelligent AI. This process would continue until one intelligence controlled everything.

This is exactly what happened in The Matrix. Humans built smart machines. Those smart machines built smarter machines that eventually came to dominate humanity.

Bostrom says that the risk of artificial intelligence is so great that the best way to prevent it from happening is to have a “control” system. This system would be a computer that would play the role of the AI. The computer would be so intelligent that it would be able to control the AI and prevent it from taking control of the world.^[9]

Do you think we could build such a control system? Or are we doomed to The Matrix?

1 Joseph Weizenbaum and the Problem of AI Empathy

Joseph Weizenbaum was the creator of the world’s first chatbot, and it was able to somewhat empathize with humans. He believed that computers would someday be able to understand human emotion and would eventually takeover service positions where empathy is necessary.

And he also believed this would be disastrous for humankind.

In his 1976 book, Computer Power and Human Reason, Weizenbaum argued that machines should never be trusted to handle delicate decision-making processes because they will always lack the wisdom, intuition, and empathy necessary to do so well.

This is what happened in The Matrix. We created machines so intelligent that they could control us, but those machines didn’t care for us—and they ultimately enslaved us.^[10]