In previous lectures, we've looked at several different notions of necessity; fate, karma, and predestination. Yet in the scientific worldview, none of these views are all that prominent. There is however, a notion of necessity that has captivated people in the scientific world, the idea of causal determinism. This means that events are inevitable because of what happened before.

The earliest known version of determinism was advocated by early Greek philosophers known as the atomists. Atomism is an extremely interesting philosophy, and many features of it were remarkably prescient in that they're similar to views that many scientists have held since the Scientific Revolution.

Soom of the key doctrines atomists promoted was that the only thing that exists were atoms and the void, which is empty space. So atoms and empty space, only. Atoms, according to the atomists, are particles that are so small that they can't be divided. So in the nuclear age, what we call atoms, strictly speaking, wouldn't count as atoms in the Greek sense, because they can be divided.

In addition to the view that all which exists are atoms and the void, a natural corollary of this is that the Gods don't exist, since there is nothing outside of the atoms and the void. This is new, given what we've seen before from the Greeks. This novel idea that there's no such thing as gods at all, but that it's just atoms and empty space.

The earliest known atomists were the Greek philosophers Leucippus and Democritus, both of whom lived in the 5th century BCE. Democritus was known as the laughing philosopher, and one theory is that this is because he regarded life with humor, since everything was meaningless. It was just these random atoms and the void.

Relatedly though, some people thought that atomism was actually a positive and optimistic philosophy, since we don't need to feat the gods or an afterlife full of pain. So we're relieved of all those kinds of worries. In a fragment from the lost work, On the Mind, Leucippus claims:

"Nothing happens at random, but everything for a reason and by necessity."

We mentioned this passage in the first lecture. This is the forst statement we have of determinism, and it captures the core idea that everything that happens, does so for some kind of reason or some kind of explanation. The atomists though, rejected the view which was then familiar, that the outcomes are a product of divine fate.

We saw these ideas reviewed in lecture two, that since they don't believe in the gods, they don't believe the gods are doing it, so fate is not responsible at all. Instead, the Atomists thought that actions, events, everything that happens, has to have some kind of natural explanation. There has to be some kind of, what we know think of as, a scientific explanation for why things happen.

The presumption was that every event has a cause. One of the statements associated with that view is that nothing comes from nothing. If you start out with nothing, then you won't get anything. Something that happens, has to come from something. It has to have some cause that's prior. When you put it like that, it seems pretty reasonable, that everything has to come from something else. So anything that happens, has to have been caused by something else.

Yet once you adopt that view, that every event has a cause, it seems like a short step to a global determinism, because what happens now has a cause, and that had a cause, and that too had a cause, so that one can just keep going! That's the idea that the Atomists were promoting, that you could just tell a causal story, all the way down.

The atomists also wanted to give a little more detail on how this was supposed to work, and they offer a really simple account of the movements of the atoms. So what they thought was that the current movements of atoms, what's happening to atoms right now, are determined by what the atoms are like. We'll use the term properties here, for what the atoms are like.

So its the properties of the atoms, and the previous movements of the atoms. To take a rough analogy, consider a pool table. Whether the balls go in certain directions, depends on the properties of the ball. Where they are, how heavy they are, those kinds of things. So it depends on that, the properties of the balls, and the immediately prior movements of the balls.

So if you want to know, say, why the seven ball went in the side pocket, you presume that the answer will be given in terms of something like where the balls were, how fast they were going, what the spin was, what the angles were, etc. Those are the kinds of things you'd appeal to, in order to explain why the seven ball went in the pocket.

That's a rough analogy to the idea that the atoms' movement are caused by the properties of the atoms, and of the atoms' previous movement. So thinking about it in terms of a pool table is actually pretty reasonable. Yet there are a couple of ways in which its disanalogous.

One is that the Atomists thought that the atoms only ever move in one direction; down. Pool wouldn't be a very interesting game, if that were the case. Yet there's a second reason why the pool analogy is inadequate. With the pool table, there are lots of possibilities for outside interference. Earthquakes can affect the balls, floods, bad construction, and of course people with pool cues.

So what happens on a pol table, is not a complete system, it's dependent on a lot of things in the outside world. Yet the Atomists thought that the entire universe is captured by their theory. There was no other force outside of the atoms, their properties, and their motions, that could interfere. The idea is that the system is complete. So there's nothing left out of the system. Everything is just the atoms and the void.

So the pool table can be thought of as an example in a kind of microcosm. If you just think about the pool table, then it's a descent analogy. Yet it has to be the pool table writ large across the entire universe.

So their idea was that everything has a kind of cause, so that in their view, there was a natural reason. Natural is a key component here, of the story, because there is another sense in which it's all random for the Atomists. So every event has a cause, yet the entire sequence is random. It's not like there's any providential reason for any of it. This is in contrast to the fate of Homer, where we think that what happens is the result of what the gods did. So here, it's random in the broad sense, and for the Atomist's there's no reason for any of it at all. It signifies nothing.

Later Greek philosophers, the Stoics, offered a different kind of determinist account. Stoicism came to prominence during the 4th century BCE with its founder named Zeno of Citium 335-263 BCE. The stoics famously maintained that one should face life with equanimity, even when under distress. They took this stoical view towards life itself. So they thought everything in life was totally determined, but this was seen as an important fact, and that we should tailor our lives in a stoical way, and repress emotions when appropriate. The latter was actually most of the time, according to the stoics.

Like the atomists, the stoics thought that every event has a cause. Yet unlike the atomists, the stoics maintained that the cause has to be rational and has to make sense in some deeper way, so that there has to be some reason why the event happened. So remember that for the atomists, the whole thing is just random in the sense that there's no rational justification. The atomists just give a naturalistic kind of scientific explanation. The stoics want something much more ambitious, and this deeper kind of explanation, this deeper reason, is given by divine providence.

So unlike the atomists, the stoics believe in the gods. So there's a sense in which the atomists and the stoics agreed with the statement that everything happens for a reason, but it's only if we think of it in terms of causal reasons. So if we return to the pool table example, we can certainly say that the atomists can certainly say, that the reason the 7 ball went into the corner pocket is because the cue ball hit the 7 and banked it off the opposite rail, or something like that.

The atomists can say something analogous about the atoms, but none of it has any deeper meaning or rational. That's where the stoics diverse, since for them, it's not enough that every event has a cause. It has to have a reason in a more full-blooded, purposeful sense. In this respect, the stoic view represents older Greek notions of fate, or on those Greek notions of fate, the older notions, the things that happen for a reason do so, because the gods make it so. They intended it to come about.

Yet as we saw with those older ideas of fate, the reason itself, need not be a good reason. For the stoics, that's required. There has to be a good reason. It isn't enough that every good event was caused. So unlike the notion of fate, the stoics maintain that the reason for an event, has to be a good reason. This is in addition to, and again unlike Homeric fate, the kind of early fate in Greek philosophy and religion. For the stoics it applies to every single thing, and not just to some special subset of our outcomes.

This kind of determinism, where everything is a product of providence, where everything happens for a good reason, can justify the stoical attitude. It makes sense to accept what happens to you, because its all part of a cosmic order that best for everyone and everything. So the stoic philosophy of life seems to fit pretty well with their philosophy of nature and the universe.

Yet there's an important concern that emerges from the fact that stoic determinism is a kind of global fate, that every event is fated. This concern was developed into an influential argument in the period that was dubbed the "lazy argument." Here's a way to put the argument.

According to stoic determinism, some people are fated to be poor, while others aren't. So we are either fated to be poor, or not. Since it's just fate, whether we'll be poor or not, it doesn't matter what we do now, because if we're not fated to be poor, we won't be poorer, regardless of whether we work hard. Yet if we are fated to be poor, we'll be poor even if we do work hard. So we might as well just relax, kick back, and see whether we'll get rich!

So that's the idea of stoic determinism, it seems like it says that whatever happens is going to happen. This is a worry, because we might think, well, does the stoic view really entail this? If so, it seems like this is a bad consequence of it.

The stoic philosopher Chrysippus 280-206 BCE, had a response to this argument, since he was concerned that this might have bad implications for stoicism. He said that some events are, what he called, co-fated. This means we won't get a certain outcome, without an earlier event.

So we might say that getting food poisoning is co-fated with eating tainted food. Whether you'll get food poisoning is fated, so that's set up from the beginning of time. Yet if it comes about, it will only be because of tainted food. There is no other way to get food poisoning.

Similarly, Chrysippus might say, being poor might be co-fated with being lazy, so that if you are lazy, then you may be more likely to be poor, since those two things go together. So Crysippus says, the lazy argument is a really bad one for trying to give you a reason to be lazy. This is because on the stoic notion of fate, you're fate is precisely a product of what happens before you meet your fate.

As we'll see in the next lecture, some philosophers think that this response to the lazy argument doesn't really get to the heart of the matter. Yet it does, as we've seen so far, serve to highlight a point about determinism that continues to be really important. The stoics use the term fate to describe their view, yet their notion of fate is very different from the notion of fate that we encountered in lecture two. On that earlier notion of fate, certain outcomes are fated, regardless of what happens before the event. It didn't matter what Oedipus did, since he would still end up killing his father. The outcome was guaranteed regardless of the causes that led up to it.

To our contemporary ears, this view sounds really implausible. Just to take a sort of easy example, if Shaun were fated to give this lecture at this time, then on that older notion which you see in the early Greeks, Shaun would still be giving this lecture, regardless of what happened before he gave it. So even if he'd been run over by a bus on his way to the studio, he'd still be giving the lecture, since it was inevitable and had to happen, no matter what. Maybe the gods would just prop him up to give the lecture?

Yet of course, to us this all sounds really unlikely. It runs counter to our everyday experience. Getting run over by a bus is exactly the sort of thing which prevents people from giving their lectures at the appointed times. Unlike this view of fate you get in Homer and the early Greeks, determinism then, whether it's atomistic or stoic fate, maintains that what we're doing right now is precisely the consequence of what happened before. So the stoics maintain that when an outcome is fated in their sense, it comes about precisely as a product of earlier fated events.

To return to the example of giving the lecture, if different things had happened when Shaun came to give the lecture, then this might have meant that he wouldn't have given the lecture. Determinism can allow all of that. It's distinguished from fatalism of this older sense, because fatalism says that certain outcomes are inevitable, regardless of what proceeds them. Determinism, atomistic determinism, stoic determinism, the next kind of determinism, as we'll see, all say that every actual outcome is inevitable, because of what precedes them. That's why they're inevitable, because of what happens before. You can't sort of take that out of the equation. That's critical.

So far, we've just been looking at notions of determinism at the early stages of philosophy. Yet in today's world, we think about determinism in a more scientific way, on the basis of views about the relationship of physical objects, in this kind of physical determinism which became really prominent in the 18th century.

So this is the prominent view of the physical world, that every physical event that happens is an inevitable consequence of the prior conditions, where the objects were and how they were moving. These prior conditions, and the physical laws, those two things together were supposed to explain why things happen. We'll say a little bit more about this as we go on.

One foundational part of the view, was the theory of physics that was proposed by Newton, which was so elegant and powerful. We all probably remember Newton's laws of motion:

1. The Law of Inertia, a body at rest will remain at rest.
2. Force = mass x acceleration, F=ma.
3. To every action, there is an equal and opposite reaction.

These are the core, but the basic physical laws like these were supposed to be complete. Newton's laws are supposed to provide a story for which one doesn't need anything else. If you want to know why a physical object moved the way it did, you wouldn't need to ask a biologist or a chemist, much less a psychologist. The whole story about how objects move, would be given by the physics.

So even for very little particles, the whole story would be given by the physical laws of motion. Nothing other than a physical event causes physical events, and physical events will always follow the law of physics. So it's important at this point to recognize that on the scientific view, everything is made up of physical particles.

Rocks, trees, guppies, and of course people. So if we have a complete story about how particles move, given by the physics, we thereby have a complete story about rocks, trees, guppies, and people. So that is the scope of determinism. That applies to everything, because it applies to the basic physical constituents, and everything is made up of these physical constituents.

This general account of physical determinism, was prominently articulated by the French philosopher/mathematician Pierre-Simon Laplace 1749-1827. It was presented in an introduction to a book he wrote on probability theory. Laplace begins his account by saying:

"We ought to regard the present state of the universe as the effect of its anterior state..."

(that is, what came before)

"...and as the cause of the one to follow." - A Philosophical Essay on Probabilities

This is the familiar way of thinking of determinism as causal inevitability. Laplace is saying that every event was caused by the event that happened before it, and it will always behave as exactly as dictated by the forces of nature. Laplace then goes on to make a colorful suggestion about what this means. He says that this has implications about the predictability of events, and he proposed a demon. That is, he said to imagine there was a demon who knew where every particle was, and he knew all the forces of nature. That demon could in principle, predict where everything would be at a later time. In a famous passage he writes:

"Given for one instant an intelligence which could comprehend all the forces by which nature is animated and the respective situation of the beings who compose it - an intelligence sufficiently vast to submit these data to analysis...for it, nothing would be uncertain and the future, as the past, would be present to its eyes." - A Philosophical Essay on Probabilities

So here we get complete predictability, according to Laplace, just like we did with divine foreknowledge. Yet now the explanation for why we're completely predictable, is completely different. The reason our actions are predictable, is because everything that happens is causally inevitable, given what happened before it. That's Laplace's suggestion, that this is entailed by determinism.

In this sense, modern determinists are much more like the atomists than like the stoics. Because unlike the stoics, modern determinists don't appeal to god or providence as directing the deterministic system. God isn't part of the equation here. This is reflected in a legendary paraphrase of exchange between Laplace and Napoleon. He gave Napoleon a copy of his book that described the system of the world. Napoleon asked how got fit into his picture, and Laplace's understated reply was, "I have no need of that hypothesis." So Laplace thought that he didn't need God to explain the universe, since the entire explanation will be given in terms of the basic laws of physics.

It'll be useful to have one last way of characterizing determinism, because philosophers have spent enormous amounts of effort, trying to get the best characterization of determinism. So here's one further way. Imagine you have two completely independent and isolated worlds, that are at a given instant in exactly the sane state. That is, they have the same number of items arranged in exactly parallel ways, with exactly the same properties.

In that case, if determinism is true, then those two worlds will be in exactly the same state at every instant in the future. The worlds will evolve or develop in exactly the same way, because the deterministic laws will operate in exactly the same ways. So this is, as we say, a prominent view after the scientific revolution, and continues to be an influential view. Why should we believe determinism? Why should we believe this thesis that everything which happens is causally inevitable, given what happened before?

Determinism is, it should be stressed, a global thesis. It says that every single event, is a product of prior events. As a result, its unlikely that any of these thinkers had adequate evidence to support their views. To be sure, the atomists and the stoics, had astonishingly little evidence. Yet this is also true of many current scientific endeavors. So if you think about the kinds of phenomena that are primarily at issue in the free will debate, we're interested in the decisions in the extraordinarily complicated organisms, us!

Even consider the complicated biological processes of digestion or the circulation of the blood. In studying these complex processes, we see, as scientists, a great deal of variation between cases. So just to take another field, think about theories of meteorology. These theories give very good weather predictions, yet they're far from perfect and there's a lot of variation.

Now that fact of variation, doesn't prove that determinism is false. There are lots of other factors involved in what determines or fixes whether or not we have the storm of a hurricane. It's possible that we just haven't identified all of the causal factors, or how their influence plays out.

Yet it's important to note that the fact that we make such good predictions about the weather, doesn't provide evidence that determinism is true regarding weather systems, because some of the remaining unpredictability might be a product of fundamental randomness. Unless you had some antecedent or prior reason for favoring determinism, you could not look at the evidence on weather data and say that something shows determinism to be true.

The fact that our theories, like those of the weather, fail to deliver perfect predictions, leaves us in a position that can be explained by both determinists and indeterminists. Determinsts say that we missed out on some on the relevant factors, and that's why eventually we should be able to get the predictions. Yet indeterminists say that the reason we're not getting perfect predictions is because there's a random element in here that we'll never going to be able to explain.

So when people do meteorology, when they try to understand weather systems, they typically reject the idea that the unpredictability results from randomness, because we assume determinism about weather systems. Yet this is not because the evidence uniquely favors it, rather it's an assumption we take when we go into the project, trying to figure out what will happen in weather systems.

So why believe determinism? Shaun thinks that the real force of determinism for these philosophers, and scientists as well, was not the evidence. It's not that they accumulated a lot of evidence and said, "See, we've shown that every single event is an inevitable consequence of what happened before it." Rather, it comes from the conviction that there has to be an explanation for anything that happens. The conviction that there has to be an explanation for anything, has guided science for centuries, and produced ample rewards.

Scientific and medical breakthroughs have been guided by the view that what we know at any given point is inadequate, and there must be a better story, theory, or medicine to be found. When we have a partial, incomplete explanation for a phenomenon, we tend to think there's still more to be discovered. We don't think, "Well, that's probably it. let's pack up our bags and go home." All this, even when we end up with an incomplete explanation.

That's probably been an important factor in what's made us so successful in science, that we've had this presumption that of course there has to be an explanation. That's driven us to look for explanations, and often those drives have born fruit. They're been really successful. So it seems like a good thing that we have this natural inclination to expect that there's an explanation. The idea that there has to be an explanation for everything is something that really resonates with us. It even resonates with very young children. Not only are children famously inquisitive, asking why all the time. Yet experimental work suggests that they naturally expect for there to be an explanation for any pattern that they see.

So for instance, in one recent experiment, children were asked questions like why a given rock was pointy? They answer with things like, "So people won't sit on it." They won't say that there's just no reason for why the rock is pointy, even though the explanation they give in that case is clearly wrong. Rocks don't emerge pointy so that people don't sit on them.

More generally, Shaun thinks, we can see the thirst for explanation in one perennial philosophical puzzle, which is why there is something, rather than nothing. Why is there anything at all? This question has led some to think that there must be a god who created the universe.

Yet if one were happy to accept things without any explanation, then there shouldn't be any pressure to explain why the universe exists at all. Nonetheless, there is considerable force to this question of why there is anything. It seems intuitively like there has to be some explanation of why the universe exists, whether or not that explanation is religious. This intuition that there has to be an explanation, might be wrong. That's not our topic.

Yet the fact that we have the intuition, suggests that we're guided by a strong expectation, that things, events, happenings, should have some kind of explanation. That, Shaun thinks, is really at the core of why scientists and philosophers have found determinism to be such an attractive doctrine. It flows from the idea that everything that happens, has to have some kind of explanation.

The doctrine of determinism continues to be quite a prominent view in the sciences. It's important to note that determinism is really a general view about systems. It's often framed in terms of physics, but one could locate determinism in more specific systems.

For instance, you think about psychology, you think about psychological processes. You could maintain that these psychological processes are determined. You could be agnostic about a lot of the rest of the world, yet maintain that every single thing that happens in your psychology, every psychological event, can be explained by appeal to other psychological events that happen before. So every decision is somehow a function of the psychological inputs to that decision.

Or you could be a determinist about biochemical processes and say that every particular biochemical event ks caused by other biochemical events. That system is deterministic. We'll see in lecture 12, that the thesis of physical determinism is under dispute in contemporary physics. The dominant physical theory of our time is no longer the Newtonian physics that inspired Laplace to be a determinist.

Rather the dominant physics of our times, as it relates to the motion of physical objects, is quantum mechanics. Yet theorists disagree about whether or not quantum mechanics requires that determinism is false. We'll look at that, to some extent, in lecture 12.

This concludes the review of the various doctrines of necessity. So we've looked at a number of different doctrines that they've developed historically, fate, karma, predestination, and now, causal determinism. For the rest of the course, we'll focus almost entirely on issues that are, when we think about determinism, almost entirely on issues related to causal determinism. Because that is the idea that really captured scientific worldviews, and has continued to exercise enormous influence in both science and philosophy.

Yet in the next lecture, we'll start looking at how philosophers of free will have responded to the threat of determinism. How they tried to address the possibility that if determinism is true, what would that mean for free will. Also, do we have reason, from thinking about free will, to reject the determinist hypothesis that we just reviewed?