Previous: Circuit Analysis: Crash Course Physics #30
Next: Outtakes #3: Crash Course Physics



View count:1,264,227
Last sync:2020-11-25 02:15
Our exploration of ethical theories continues with another theistic answer to the grounding problem: natural law theory. Thomas Aquinas’s version of this theory says that we all seek out what’s known as the basic goods and argued that instinct and reason come together to point us to the natural law. There are, of course, objections to this theory – in particular, the is-ought problem advanced by David Hume.

Get your own Crash Course Philosophy mug or Chom Chom shirt from DFTBA:

The Latest from PBS Digital Studios:


Produced in collaboration with PBS Digital Studios:


Want to find Crash Course elsewhere on the internet?
Facebook -
Twitter -
Tumblr -
Support CrashCourse on Patreon:

CC Kids:

Hank: Thomas Aquinas was no dummy. Remember him? The Italian fella? Christian monk? Philosophical superstar of the 13th century? Aquinas thought morality was important for everyone, and that being a good person was a vital part of God’s plan for each of us. But he knew that not everyone had been exposed to the Bible, or had even heard of God.

So, what bothered him was: How could people follow God’s moral rules – also known as the divine commands – if they didn’t even know about the guy who made the commandments? Aquinas just couldn’t believe that God would have expectations for us, if he didn’t also give us – all of us – a way to meet them.

So, Aquinas’ theorized that God made us pre-loaded with the tools we need to know what’s Good. This idea became known as the natural law theory. And there are a lot of versions of this theory still circulating around today. But Aquinas’ original take on natural law is by far the most influential, and the longest standing.

How influential? Well, if you’re Catholic or a member of any of the major Protestant denominations, or were raised in any of those traditions, then you’re probably already familiar with how Aquinas saw the moral universe and your place in it. Basically, God is awesome, and he made you, so, you are awesome. It’s just important that you don’t forget to be awesome.

[CrashCourse intro plays]

We all want stuff, Aquinas got that. And he said that it was OK. In fact, the theory of natural law is based on the idea that God wants us to want things – specifically, good things. Aquinas argued that God created the world according to natural laws: predictable, goal-driven systems whereby life is sustained, and everything functions smoothly. And as part of this natural order, God made certain things that were good for his various creatures.

Sunlight and water are good for plants. Meat is good for cats, and plants are good for bunnies. And – because God is awesome – he instilled all of his creatures with an intuitive desire for the things that he designed to be best for them.
The things that we’re designed to seek are known as the "basic goods," and there are seven of them.

The first thing that all living things just naturally want, Aquinas said, is self-preservation – the drive to sustain life. Aquinas thought God built all creatures with a survival instinct, and this appears to be pretty much true. I mean, we naturally avoid dangerous situations like swimming with hungry sharks, and when we find ourselves in danger, we don’t have to stop and ponder the options before getting ourselves to safety.

After preserving our own lives, our next most pressing basic good is to make more life – in other words, to reproduce. Some beings are able to do this on their own, but since we need to coordinate matters with a partner, God kindly instilled us with a sex drive, and made the process feel good, to make sure that we do it. Thanks, God!

But once we manage to achieve our second basic good – reproduction – we need to educate those kids we just made. For humans, that’s going to mean stuff like school and lessons in morality. But even non-human animals need to teach their babies how to hunt and avoid predators. Otherwise, the offspring they worked so hard to create aren’t going to survive long enough to reproduce themselves, which, of course, is the goal of everything.

And while these first goods seem to apply to a pretty wide swath of creation, some of the basic goods are just for humans, because of the particular kind of being we are. For instance, Aquinas thought we are built with an instinctual desire to know God. He believed we seek him in our lives, whether we’ve been exposed to the idea of God or not. Interestingly, the existentialist Jean-Paul Sartre agreed with Aquinas on this. He said we’re all born with a god-shaped hole inside of us. The tragedy, for Sartre, is that he was an atheist, so he believed this was an emptiness that could never be filled.

Next, taking a page out of Aristotle’s book, Aquinas also said that humans are naturally social animals, so it’s part of our basic good to live in community with others. While short periods of solitude can be good, he believed that we’re basically pack animals, and our desire for love and acceptance, and our susceptibility to peer pressure, are all evidence of this.

Now, since we naturally want to be part a pack, it’s a good idea not to alienate our pack-mates. So, basically, Aquinas said we recognize the basic good of not pissing everybody off. I mean, he didn’t actually say it that way, but if he did, I’m sure it sounded a lot better in Latin. The point is, Aquinas said we feel shame and guilt when we do things that cause our group to turn against us, and that was another basic good.

And finally, Aquinas said we’re built to shun ignorance. We’re natural knowers. We’re inquisitive, and we want to be right. This is another trait we share with non-human animals, because knowledge promotes survival, and ignorance can mean starving to death or ending up as someone else’s dinner.

So these are the basic goods, and from them, we can derive the natural laws. We don’t need the Bible, or religion class, or church in order to understand the natural law, Aquinas said. Instead, our instinct shows us the basic goods, and reason allows us to derive the natural law from them. Right acts, therefore, are simply those that are in accordance with the natural law.

So how does this whole system work? Well, I recognize the basic good of life, because I value my own life. And that’s clear to me, because I have a survival instinct that keeps me from doing dangerous, stupid stuff. Then, reason leads me to see that others also have valuable lives. And from there I see that killing is a violation of natural law. So, for each negative law, or prohibition, there’s usually a corresponding positive one – a positive injunction.

For example, "Do not kill" is a prohibition, but there’s also a positive injunction that encourages us to promote life. And I can take that positive injunction of promoting life to mean anything from feeding the hungry, to caring for the sick, to making healthy choices for myself. And we could do the same thing with each of the basic goods.

The basic good of reproduction leads to a prohibition, don’t prevent reproduction, which is why the Catholic Church has been opposed to birth control. And the positive injunction there is: Do procreate! Do all the procreating you want! And if you think it through – using your God-given reason – you’ll be able to see how the other natural laws are derived from the basic goods.

But, of course, as with the Divine Command Theory, the theory of Natural Law raises plenty of questions. For example, if God created us to seek the good, and if we’re built with the ability to recognize and seek it, then why do people violate the natural law all the time?! Like, if this is supposed to be something so intuitively obvious that even plants and non-human animals can manage it, why is the world so full of people-killing and offending others and folks who do everything but seek God?

Aquinas had two answers for this: ignorance and emotion. Sometimes, he said, we seek what we think is good, but we’re wrong, because we’re just ignorant. And yes, that happens. I mean, there once was a time when cigarettes were literally what the doctor ordered. Back then, we thought we were promoting our health, but we were actually hurting it. No matter how awesome God made you, or your desires, you have to have some understanding of how to be awesome.

But ignorance can’t account for all of the stupid things we do. Aquinas, again following Aristotle here, said that, even though we’re rational, we’re also emotional creatures. And sometimes, we see what we should do, but emotion overpowers our reason, and we fail to do the things we know we should.

So, in those cases, we just kinda forget to be awesome. Now, as with the Divine Command Theory, Natural law gives us a handy answer to the grounding problem. It tells us that morality is grounded in God, that he created the moral order.

It also gives us a reason to be moral – following the natural law makes our lives work better. But while it seems to have a lot more going for it than divine command theory, natural law theory has its share of critics as well.

First of all, it’s not going to be super appealing to anyone who doesn’t believe in God. You can tell me God set the world up according to natural laws, but if I reject that whole premise, there’s not a lot you can do to convince me. Another objection comes from 18th century Scottish philosopher David Hume, in the form of what’s known as the is-ought problem. And to investigate this, let’s pop over to the Thought Bubble for some Flash Philosophy.

Hume said it’s fallacious to assume that just because something is a certain way, that means that it ought to be that way. But that’s basically what natural law theory does all day long. We look at nature and see that creatures have strong survival instincts, so from there we conclude that survival instincts are good.

But, are they? I mean, to me, yeah, because it helps me stay alive. But my survival instinct could also cause me to do all sorts of things that look immoral to other people. Like killing you and crawling inside your still-steaming body, tauntaun-style, to stay alive in a blizzard. Not that I would do that, but just for example.

Likewise, we can observe the existence of sex drives and conclude that reproduction is good. But, sexual drive is also used by bad people to excuse horrible immoral things, like committing sexual assault. And for that matter, is reproduction always good? Is it something all beings have to do? Am I sinning if I choose never to have children? And what about bodies that can’t reproduce? Or people who don’t want to reproduce or have partners that they can’t reproduce with?

Thanks, Thought Bubble! As you can see, for all it has going for it, natural law theory can pretty quickly open some big ol’ cans of philosophical worms. Which might be why 18th century German philosopher Immanuel Kant thought we needed a better option. Which we’ll consider next time.

Today, we learned about natural law theory, as proposed by Thomas Aquinas. We studied the basic goods and the way instinct and reason come together to point us to the natural law. We also discussed some problems with the theory, in particular, the is-ought problem advanced by David Hume.

Crash Course Philosophy is produced in association with PBS Digital Studios. You can head over to their channel to check out a playlist of the latest episodes of shows like Blank on Blank, Braincraft, and Coma Niddy. This episode of Crash Course was filmed in the Doctor Cheryl C. Kinney Crash Course Studio with the help of these awesome people and our equally fantastic graphics team is Thought Cafe.