Christian Apologetics - Lesson 17

Possible Worlds (Part 1/2)

A possible world is a way the real world could have been. Modal logic, propositions, state of affairs and eternal entities are some of the considerations when discussing a possible world.

Ronald Nash
Christian Apologetics
Lesson 17
Watching Now
Possible Worlds (Part 1/2)

Possible Worlds

Part 1

I.  Introduction

A.  Modal Logic

1.  Traditional - Two-Value Logic

2.  Modality - Three-Value Logic

B.  Propositions

1.  Relationship to a sentence

2.  Relationship to truth

C.  State of Affairs

1.  Relationship to a proposition

2.  Converting a proposition to a state of affairs

D.  Eternal Entities

1.  Every true proposition is eternally true.

2.  States of affairs are eternal entities.

  • Introduction to Apologetics.

  • Apologetics involves finding evidence and presenting arguments to defend the Christian faith.

  • Two prominent worldviews are Christian theism and naturalism.

  • The law of non-contradiction states that A cannot be B and non-B at the same time and in the same sense.

  • Explanations and responses to different worldviews.

  • If God is good and all powerful, then why does evil exist?

  • Discussion about how the existence of evil is consistent with God's character.

  • Your noetic structure, presuppositions and view of epistemology are important elements in the formation of your worldview.

  • Discussion of deductive presuppositionalism vs. inductive presuppositionalism.

  • Objections to inductive presuppositionalism.

  • Arguments for and against evidentialism.

  • Arguments for and against foundationalism.

  • Discussion of natural theology.

  • There are valid, sound and cogent arguments for the existence of God, but no coercive proofs.

  • Discussion of different arguments for God's existence.

  • One version of the cosmological argument for God's existence emphasizes God as first in time, another emphasizes God as first in importance.

  • A possible world is a way the real world could have been. Modal logic, propositions, state of affairs and eternal entities are some of the considerations when discussing a possible world.

  • Something is logically possible if its description does not include a logical contradiction. The existence of the laws of knowledge refute the system of naturalism.

  • Middle knowledge is a form of knowledge attributed to God by Molina.

  • Miracles are a dividing line and central to Christianity.

  • David Hume's rational arguments against miracles and responses to those arguments.

  • Two miracles central to Christianity are the incarnation and resurrection.

  • The question of whether or not Jesus is the only savior touches on pluralism, inclusivism and exclusivism.

  • Pluralism is the view that all religions have salvific value.

  • Inclusivism is the view that even though the work of Christ is the only means of salvation, it does not follow that explicit knowledge of Christ is necessary in order for a person to be saved.

  • Salvation is totally the work of God and all children who die in infancy are elect of God.

  • Discussion from a biblical perspective of God's character and attributes.

  • Open theists believe that God does not have a perfect knowledge of the future.

  • Divine omnipotence and divine omniscience are two attributes of God.

  • When contemplating life after death, remember, Jesus has been there and come back. Will you commit your life to him or reject him?

These lectures were given at Reformed Theological Seminary in Orlando, Florida during the fall of 2001.


Dr. Ronald Nash
Christian Apologetics
Possible Worlds (Part 1/2)
Lesson Transcript


[00:00:18] Possible worlds. That's the topic of Chapter nine. Two little stories. Story number one, I was teaching this course during a one week span of time in Charlotte. Oh six, seven years ago before I had put any of this stuff in print. And, you know, taking any course in five days can be very tough. So the last day of class, I announced that I was going to talk about the doctrine of possible worlds the entire week there, there there was a mother in that class who really was the best she was. She was miles ahead of the fellows in that particular class. I won't mention her age because she might someday listen to this particular tape. Okay. But when I announced that I was going to talk about possible worlds, she said out loud. Oh, good. I was hoping you do that. That's really the reason I took this course. Okay. It seemed that her eldest oldest son was a philosophy major at a college that I will not identify. And he was planning to go on to a get a Ph.D. in philosophy. And he was all involved in this possible world stuff. And she wanted to master it so they could talk the same language over breakfast. See, that's true story. Second story, we go up a little bit. I was this part of the story I think I was. I once served as president of the Kentucky Philosophical Association. Now, give me a big who say that louder. So the tape will pick that up. Oh, the Kentucky Philosophical Association will be well as president. I got to plan one of the two meetings that we have. So I said, as president, we're going to have this meeting on my campus and I'm going to pick the speaker. And you all are going to have to come and listen to the guy that I want to speak. All right. And I picked Al planning. So we met in a and what the CFPA was and is is an association made up of many of the professors of philosophy in the state of Kentucky. So we had maybe 30, 35 PhDs in philosophy in attendance. And we met in a fairly small room on the campus of Western Kentucky University. And I because I introduced Al planning a, I then sat behind him on the platform while he read his paper. So I had a chance to observe the audience. And I knew I knew that not one philosophy Ph.D. in that audience understood a thing, the planning I was talking about. Now. Of course I did. No, I didn't either. All right. Nobody understood a thing that he was talking about and planning. I used to do that. See? Because it's called intimidation. It's called intimidation. When when you know, there are a lot of philosophers who are kind of arrogant. Now, I know you've never met one. All right. And there are other philosophers that have chips on their shoulder. And you've never met anybody like that, either. But when a philosopher doesn't understand somebody, he tends to think that just maybe this guy is smarter than he is. And that's what planning a did for a period of some ten or 15 years until he gained a reputation and people began to think that this guy is pretty good. And that's when he started to articulate his apologetics and his defense of the Christian faith after the meeting. Long story here. After the meeting, one of my colleagues in my department was trying to make small talk with planning and said something like this. What do you regard as the most important thing you're working on now when you're in the presence of someone whom you don't understand? That's not a bad question to ask, right? There are other. How's your family? What do you think about our weather today? And here's what planning has said. And this was not his subject that day. I I've actually forgotten what he what his subject was. He said, I've gotten very interested in quantified moral logic, and I honestly believe that has the potential to be one of the most exciting new branches of philosophy in centuries. Okay. Well, today I'm going to introduce you to a quantified moral logic. If you want to say thank you, Doctor Nash, You okay? One more story. Yeah, why not? Just to show that you understand this is important. My pastor, my previous pastor. Bill Haynes once stopped me at church and he said, Do you ever talk about. Metal knowledge. I said, Yeah, can you give me a little introduction of middle knowledge? I said, Yeah, but you can't understand middle knowledge, the middle knowledge of God unless you understand possible world. So if you come to my apologetics class this day of the week, in 2 hours, first hour, I'll introduce you to possible worlds. The second hour, I'll tell you everything you need to know about middle knowledge, he said, will be there. And he brought one of his staff members. Okay, So. All over America. There are people who flock to this cause. And the reason why this room is not as full as it would ordinarily be is because I didn't know until this morning that I was going to talk about possible worlds. If I'd gotten on the phone, people would have flown down here today just to hear me talk about quantified mortal logic. And I'm kidding, of course. All right. So open your textbook if you brought it. I realize you may not have, but open your textbook to chapter nine Possible worlds. And if you'll forgive me, I'm just going to go through the text and I'll. I'll take the topics in the way they in the in the chronology in which they appear. But I'll just explain them extemporaneously using probably different examples and so on. What is modal logic? Prior to this new interest in modality, traditional logic has been what we call a to value, logic to value. In other words, propositions are either now this is modality over here, this is more traditional logic. It has been a to value logic. True or false? Those of you who have more training in mathematics than I do. The more technical word would be binary. And of course, I almost feel embarrassed to tell you what I know. You already know A kind of binary logic is really the foundation of all of our computers. All right. It's. It's one or zero. Open or closed. And what you do on the basis of a binary system is you just, you know, develop programs and so on. And that's that's the way computers work. True or false? True or false? Many of my quizzes are binary in nature. True or false? Now what is modality? Well, philosophers. And of course have known about modality and its importance for several hundred years. For example, a German philosopher, Linus, did a lot of work on modality. But we've had a revival of interest in in modal logic in the in the 20th century, because this deals with this gives us a three value logic. We can not only talk about propositions that are true and propositions that are false, but we also want to deal with such concepts as and this is the third modality here. Okay. Necessity. Possibility and impossibility. Now, I know I've written three key words on the board, but it isn't those three words that make this a three value logic. All of these are. That is, necessity. Possibility and impossibility are examples of modality. You see some propositions are contingently. True. As in the case of the proposition that on October 30th nine, 2001, Ron Nash is 65 years old. All right. But other propositions are necessarily true. It is contingently true that Ron Nash is 65, but things could have been different. He might have been born a year earlier. He might have been born a year later. He might not have been born at all. What an interesting world that would have been. Okay. But other propositions aren't necessarily true. Two plus two equals four. Five plus five times five is 25. That's not just contingently true, that's necessarily true. And other propositions are impossible. That cannot possibly be true. So. Once philosophers began to focus on the UN, on the matter of necessity. Impossibility, possibility and related notions. It occurred to somebody that thinking in translating modal logic into the language of possible worlds could make it easier to understand all of this stuff. Okay. Now, I explain that the doctrine of possible worlds is a heuristic device. I don't ever encourage think of some of the heuristic devices that were used in your case, in your education during, let's say, high school. People have developed models of the solar system. I suppose I saw my first model of the solar system in the fourth or the fifth of the sixth grade. You know, there's there's something there that resembles the sun and so on. Or else you get a professor in a chemistry class who gives you a stick. And on one end there are two blue balls, and on the other end there's one red ball. And that's a heuristic device that helps you visualize or model a molecule of water H2O. Well, a heuristic device is a teaching tool. It would be a mistake, probably a serious mistake if you interpreted everything we say about possible worlds in a literal way. I'd like to see even an open theist interpret the doctrine of possible worlds in a literal or straightforward way. So that's what we're going to be doing. Now let's go right through the text and we'll take the sections as they are, because I can't think of a better way to organize this material than what I give you here. First of all, I ask the question, What is the proposition? What is a proposition? And that question invites you to think about the difference between a sentence and a proposition. What is a sentence? Well, it's a collection of words or symbols that represent words. That. Say something. Presumably, although some sentences can intentionally be nonsense. All right. A proposition is best understood to be the meaning of any sentence. For example. Let me give you two sentences. John is the husband of Mary. That sentence one sentence to Mary is the wife of John. No one would ever deny that. These are two different sentences. However, they both have the same meaning or they both refer to. Here's another way of saying this. They both refer to the same state of affairs. And so philosophers, when they talk about a proposition, they seldom are foolish enough to confuse a proposition with a sentence. Rather, a proposition is the meaning of a sentence. Okay. And so when we talk about the truth. Are involved in what we say. Truth is a property of proposition. Now, this leaves us with, you know, a proposition. And this in this way is kind of a mysterious entity. It. It has a strange ontological existence in the universe because it's not strictly identifiable with any particular sentence. Here. Here would be one other example. Consider the English sentence. It is raining. Now I'm going to ask Alicia to give me this meaning in Swahili. See, that's exactly what I would have said. Thank you. All right, somebody say this. Don't. Don't. But if you say this in French or German. Or Spanish. What you would have would be different sentences, but the meaning would be the same and the proposition. I mean, if we have five people each speaking a different language. Ordering a different sentence, they would still be referring to the same proposition. Are you with me? Say yes. Okay. Now let's move then, to a state of affairs. We now want to make a distinction between a proposition and a state of affairs. But in doing this, we may refer to the proposition with just a sentence. All right. We you know, this is a funny relationship here. Now, I don't want to write all of this on the board because I would lose a lot of time here. So if you'll just look at the textbook page 210 with me. What I give you on the left hand side of the page is a proposition. But on the right hand of the page, I give you a state of affairs. Here is Proposition one that we're going to consider. George W Bush is president of the US in 2001. There, that's a proposition. Fortunately for the world, it's a true proposition. Amen. Now, what's the corresponding proposition? George W Bush's being president. And then you can finish. You know, in the of the US in 2001. Now, there's a very simple way in which you convert. I hope you're getting all of this in your notes. It's a very simple way by which you convert a proposition to a state of affairs. First of all, you make the subject of the sentence possessive. Okay. George W Bush becomes George W Bush's. And then you changed the verb to a gerund. Okay. And the gerund of is is the word being. George W Bush's being president of the United States. Here's proposition number two. And I'm not going to write this on the board. The proposition is the Florida marlins won the 1997 World Series. Oh, yes, Ronald, these examples have got to go. If you don't know who what team they beat in 1997, it was a team from Cleveland. All right. Flunky. Florida marlins. All right. Now, how do you turn that proposition about the Florida marlins? Here's how you make the subject possessive. The Florida marlins and you change the verb win to winning. You change it to a gerund. Okay. And then finally, my final example. The Soviet Union ceased to exist in 1991. That's another true proposition. And the corresponding state of affairs is the Soviet Union's ceasing to exist in 1991. Notice for every proposition there is a corresponding state of affairs. What is the state of affairs? It is that reality which is referred to by the proposition. Now, one more thing about states of affairs when a proposition is true. The corresponding state of affairs we say obtains. Okay. In 1997, when the proposition the Florida marlins won the World Series was was true. The corresponding state of affairs obtained when a proposition is false. We say that the state of affairs did not obtain. It's simple. In fact, several times here in this book, I say a lot of people find this stuff difficult, but it isn't difficult. It really is just a matter of common sense. All you really have to do is learn the definitions, learn the terms we're using. Get them in your notes and memorize them, and you'll be able to talk like this. Okay. Now, the next point, the claim at the top of page 211 that propositions and states of affairs are eternal entities. Now I know. And thus I say in the book, this blows some people's minds. It shouldn't. If you've taken the history of philosophy course here and you agreed to some extent with Plato and the Augustan. That there are that there isn't a we're a world of eternal and unchanging essences and so on. What we're saying here is not that difficult. We talked the other day in this class about the number one being eternal. I know some of you may have had a little trouble swallowing that, but just try to live with the denial of that. All right. If the number one isn't eternal. When did it start to exist? Now. Every true proposition. Is eternally true. Let's take some examples. A better a happier example. The proposition. The Cleveland Indians won the 1948 World Series. Okay. That, of course, happened in an earlier century. Do you know that that proposition is eternally true? Now. Why? What does it mean to say that a proposition is eternally true? It simply means that that proposition has always existed in the mind of God. That's all. Let me see. Now, let's take another example. The Pythagorean theorem. In the case of a right triangle where A is one side, B is the other side, and C is the hypotenuse. A squared plus B squared equals C squared. And we could put that in the language, you know. But that proposition has been eternally true. But some people might object. What about the proposition Ron Nash is typing or Ron Nash is eating? That proposition cannot be eternally true. To which here is my answer. Yes, it can be. When you formulate that proposition correctly. See. Strictly speaking, the proposition Ron Nash is typing is not a well-formed proposition. It's an open statement, but once we close the open parts of it, then we get a properly formed proposition. Here's what I mean. If you if you close all of the windows and I don't mean this in a microsoft kind of way. If you eliminate all of the indeterminate elements of that sentence in and here's how you do it. Ron Nash is typing when. On October 30th, 2001, at 1:33 p.m. Eastern Standard Time. Where. In his office at 774 High Grove Park Court. Oviedo, Florida Planted Earth. Okay. When you close all the gaps, you've got a proposition that is eternally true. And one of the ways to understand that is that God has always known. But at that time and in that place, Ron Nash would be typing or, you know, eating potato chips or watching a baseball game on television or teaching a class of ecstatic, enthralled, mystically elevated students. God has or God always knows. All true propositions. Including those about the future. Now. Right now, Nash's thumbing his nose at the open theists. Who say poor God can't know the truth value of future propositions. Why? Because propositions about the future have no truth value. No. You want what will argue that someday, but not now. Okay. So. Propositions are states of affairs. I'm sorry, propositions are eternal entities, and likewise states of affairs are eternal entities. Let's consider the state of affairs. George W Bush's being President of the United States on planet Earth. On October 30th, 19 I'm sorry, 2001. That state of affairs is eternal. It has always existed. And if you're having trouble with that, sign up to take the history of philosophy course the next time it's offered. Okay. Because we give you the foundations of that when we talk about Plato and Augustine.