Week 1 - What is Evidence? (Dec 6)

Week 1 Resources

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Week 1 Notes

First, a quick overview of what we will cover in this class. Today, we are going to talk about what it means to have evidence for Christianity. Starting next week, we will go over 4 arguments for God’s existence in detail. This will take about four weeks. We will go into detail about how the beginning of the universe demonstrates the existence of a supreme creator. We will also see how the Universe is fine-tuned for life in an extremely precise way. Furthermore, we will discuss how genetics and intelligent design lends support to the existence of God. Finally, we will talk about the moral argument for God’s existence. 

Then for three weeks we will go in depth on the evidence for Christ’s resurrection from the dead. We will talk about all the main sources for that event. We will also talk about alternative theories to the resurrection. And finally we will spend the last week of our resurrection study talking about how likely the resurrection is, given the background information and the evidence. 

In the last few weeks, we will talk about common objections to Christianity, and the specific answers that they have. For example, some people say that Jesus never claimed to be God, and that the Christians just made that up after the fact. Others say that the idea of Jesus dying for our sins doesn’t make sense. How is it justice for an innocent man to be punished for our sins? We will also talk about why there is so much pain in the world, if God exists. We will also talk about why God seems so hidden. After all, if God wanted everyone to believe in him, wouldn’t he make himself obvious? 

This class will actually have a website and a Facebook group associated with it, so that you can access the resources to the class more easily. It will have the link to the Facebook group in there too. 

I will post to the blog every week, a few days after the class. On that blog you will find a summary of the previous week’s material. Furthermore, you will see resources for the upcoming week, to get a head-start on the upcoming week’s material. Usually, I’ll send out a five or ten minute video that will give you a taste of what we will be talking about the following week. I’ll also post resources on each subject, in case you want to dive much deeper into a particular subject matter. For example, I post some solid books and articles on the topic, so you can go deeper if you want to. 

This class is called “Evidence of Christianity.” But we really need to break that down first. First, Is Christianity something we need evidence for? Second, what is “evidence?” 

Someone read 1 Corinthians 15:13-19:

13 But if there is no resurrection of the dead, then not even Christ has been raised. 14 And if Christ has not been raised, then our preaching is in vain and your faith is in vain. 15 We are even found to be misrepresenting God, because we testified about God that he raised Christ, whom he did not raise if it is true that the dead are not raised. 16 For if the dead are not raised, not even Christ has been raised. 17 And if Christ has not been raised, your faith is futile and you are still in your sins. 18 Then those also who have fallen asleep in Christ have perished. 19 If in Christ we have hope[a] in this life only, we are of all people most to be pitied.

According to Paul, should we still be Christians if Jesus is dead? Why not? 

It’s interesting that Paul writes this part right after giving evidence for the resurrection. Can someone read 1 Corinthians 15:3-8. 

3 For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, 4 that he was buried, that he was raised on the third day in accordance with the Scriptures, 5 and that he appeared to Cephas, then to the twelve. 6 Then he appeared to more than five hundred brothers at one time, most of whom are still alive, though some have fallen asleep. 7 Then he appeared to James, then to all the apostles. 8 Last of all, as to one untimely born, he appeared also to me.

Does Paul think that we should have evidence for our faith? Or does he think we should just believe it, with no evidence?

Since we do have evidence, what good would that do for us? What’s the benefit of talking about what evidence we have for our faith?

Could someone read Luke 1:1-4:

1 Inasmuch as many have undertaken to compile a narrative of the things that have been accomplished among us, 2 just as those who from the beginning were eyewitnesses and ministers of the word have delivered them to us, 3 it seemed good to me also, having followed all things closely for some time past, to write an orderly account for you, most excellent Theophilus, 4 that you may have certainty concerning the things you have been taught.

Ok so this is Luke’s intro to his Gospel. Why is Luke writing? Can we read that last sentence again? Studying the evidence for Christianity gives us certainty in the face of doubt. It gives us strength, in the event that doubts come along, and they sure will. It serves to strengthen our faith. 

Can someone read 1 Peter 3:15

but in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect,

Knowing the evidence helps us give a defense for when someone asks why we believe what we believe. It serves an evangelistic purpose then, since the evidence can serve to sway someone to believe in Christ. 

Inductive Reasoning

But what is “evidence” in the first place? For example, if I’m in my house, and I smell smoke, is that evidence that the house is on fire? Is it proof that the house is on fire? Is it strong enough evidence to actually believe that the house is on fire? 

Now let's take another example. Suppose that I smell smoke, and my roommate yells “fire!” Is that evidence that the house is on fire? Is it proof? Is it enough evidence to believe that it is on fire? 

Now, I can think of a situation where the roommate would yell “fire” and I would smell smoke, but the house is not on fire. For example, maybe a friend was over using the microwave, and burnt some popcorn. At the same time, maybe he was doing target practice with a nerf gun. Maybe he yelled “ready, aim, fire!” right as the popcorn was burning. But I think we’d all agree, the evidence that the house is on fire is a lot stronger in this situation, than a situation where we just smell smoke. 

Now imagine another situation. Imagine I am in my room, and I smell smoke. The roommate yells “fire” from the other room. I touch the surface of my door, and it’s hot to the touch. Now, do I have proof that the house is on fire? What about strong evidence? Is it enough to believe that the house is on fire? 

What we are doing is viewing evidence as a symptom of something. We start off in our minds, and we realize that the house is not usually on fire. In fact, there is a very low probability that the house is on fire. However, things like smoke raise the probability that it's on fire, even if it doesn’t prove it. Similarly, additional pieces of evidence, like the roommate yelling “fire!,” raise the probability even more.

In this situation, the evidence has a strong cumulative effect. Maybe each piece of evidence isn’t conclusive by itself. But together, they make a very powerful case. 

Little pieces of evidence can stack up very quickly. Here’s another example. 

Let’s say that I have two bags that look identical. One has 75 red marbles and 25 green marbles. The other has the opposite. 75 green marbles, and 25 red marbles. We shall call the first bag the "mostly red" bag. The second bag is called the "mostly green" bag.

You hide both the bags behind your back, and then give me one. I do not know which bag you have given me. I pull the first marble out, and it is green. I then put it back in, and pull another marble out. This time it is red. After drawing and replacing marbles 13 times, I record 8 red marbles and 5 green marbles.

Now two questions.

Question 1: What bag am I probably holding?

Question 2: What is the probability that I am holding that bag?

Now, I’ve pulled 5 green marbles and 8 red marbles. So I pulled a total of 13 marbles. Now you might think that the odds that I chose the “mostly red” bag to be 8 divided by 13 or 61%. After all, there are only 3 more red marbles than green marbles. 

However, there is actually an equation we can use to model this. We won’t do this today, but according to the equation, the probability that we chose the mostly red bag is above 96.4%. It is 27 times more likely that I am holding the “mostly red” bag than the “mostly green” bag. But why? Each green and red marble cancels each other out. But the three red marbles that don’t have corresponding green marbles are not simply added together. They are actually multiplied together. 

The moral of the story is, that little pieces of evidence can really add up to something big, when taken together. This may seem really abstract right now, but this way of looking at evidence will be really important, especially when we discuss the resurrection of Jesus, and the fine-tuning of the universe. The fact that evidence adds up to something bigger than meets the eye, plays a really big role in understanding evidence for Christianity. 

For example, each disciple of Jesus was a witness of him after he had resurrected. Maybe one disciple can be mistaken or lying. But if each disciple is, say, 85% reliable, the value of their testimony multiplies out to a very high number. Multiply that by all the disciples, and you got some serious evidence stacking up. 

Just think of evidence this way. Suppose we smell smoke. We are surprised by that, since we don’t usually smell burning. However, if the house was on fire, we would not be surprised if we smelled smoke. Therefore, if we find something surprising, but unsurprising if the hypothesis is true, then we have evidence of something. 

This is why it's kind of crazy when people say there is no evidence of God’s existence. For example, we will see that a fine tuned universe is surprising on the view that there is no God. It is less surprising that we would find a fine-tuned universe given that God does exist. 

For example, cosmologists know that the universe has been expanding since its beginning. However, if at the beginning of the universe, someone added a dime’s mass to it, the universe would expand too slowly, and no life would exist. On the contrary, if someone had removed a dime’s worth of material from the beginning of the universe, it would have expanded too fast, and no life would exist. This is something that is surprising if there is no God, but less surprising if there is one. Therefore, it counts as evidence for God’s existence. 

The type of reasoning we have been discussing so far is inductive reasoning. This is where we observe a sample of something, and then generalize to a whole based on that. For example, if we take a bag of coins, and pull out three of them, and they are all pennies, that is evidence that the whole bag is pennies. 

Same with the bags of marbles. We are generalizing to the whole bag, based on just pulling a few marbles out of it. We are taking some specific piece of inductive evidence, and generalizing to the whole bag based on that. 

Just like we saw with the house on fire example, inductive evidence doesn’t prove something. It only makes it more likely. As we saw with the marbles example, the strength of evidence can multiply very quickly. 

Inductive reasoning is important. It can help us provide evidence for premises in a deductive argument. Now that we have talked about inductive reasoning, we will now talk about deductive reasoning. 

Deductive Reasoning 

A deductive argument is different from an inductive argument, in that if all the statements in the argument are true, then the conclusion has to be true. For example, 

  1. All men are mortal

  2. Socrates is a man

  3. Therefore, Socrates is mortal 

This is called a logical syllogism. If the premises are true, and the argument is valid, then the conclusion has to be true.

This is called “modus ponens.” It goes like this 

P implies Q



Now this is always true, given that the premises are true. However, it does have to be valid. There are versions of this argument which are not valid. For example,

  1. All men are mortal

  2. Socrates is mortal

  3. Therefore, Socrates is a man 

This is a formal fallacy called affirming the consequent. It goes like this:

P implies Q




Notice the difference? In the first case, we determined that Socrates was mortal because all men are mortal. In this case, the invalid argument is saying that Socrates is a man, because he is mortal. That’s not true, because animals are mortal as well. The class of mortal things is larger than the class of things that are men. In this case, the conclusion does not follow even if the premises are true. 

Now an argument can be logically valid, but have false premises. For example:

  1. If Socrates is a man, then he is a monkey's uncle.

  2. Socrates is a man.

  3. Therefore, Socrates is a monkey's uncle.

Is this argument valid?

This argument is valid, meaning that if the premises are true, the conclusion has to be true. But clearly in this case, the premises are controversial! Most of us would not agree with the first premise. Therefore, although the argument is valid, it is not sound.

Now some premises are determined through inductive reasoning. For example, we know that all men are mortal, because of observation. Perhaps there is some man somewhere that is not mortal. But of all the men we have observed, all of them are mortal. Therefore, we take the statement “ All men are mortal” as more plausibly true than not.

Deductive reasoning is very important for some arguments for God’s existence, as we will see next week in particular.  It’s also important to understand this, because some arguments against God’s existence will also take this form. Next week we are going to talk about one of the strongest arguments for God’s existence, which is a deductive argument that takes this form. To give you a preview, the argument goes like this:

For example, take the following syllogism:

  1. If the universe began to exist, then the universe has a cause

  2. The universe began to exist

  3. Therefore, the universe has a cause 

Is premise 1 true? Well we know from inductive reasoning, that things don’t just pop into being out of nothing. Every time we observe something coming into existence, it has a cause. So why would the universe be any different? After all, if whole universes can come into being out of nothing, then why don’t horses, chairs, and root beer do this all the time? So we take the first premise as more plausibly true than not.

What about premise 2? Well science tells us that the universe had a beginning. Furthermore, there are philosophical reasons for thinking that time had to have had a beginning. We will explore these in detail next week. So because of science, we will accept that the universe had a beginning. 

Therefore, the universe had a cause. What kind of cause would the universe have to be? Since the cause created all time, space, matter and energy, it would have to transcend those things. It would have to be timeless, spaceless, immaterial and incredibly powerful. As we will see next week, the cause also has to have free will. 

So we can see the importance of understanding deductive arguments for making arguments for God’s existence. 

So far, we’ve seen that there is inductive reasoning, as well as deductive reasoning. But there is one more type of reasoning, called abductive reasoning. This is also called “inference to the best explanation.” 

Abductive Reasoning

Sometimes, we can’t use inductive reasoning or deductive reasoning. In some cases, we have to judge between 2 or more competing theories, and see which is best. But how do we know which theory is best? In this case, we have to use abductive reasoning. Abductive reasoning is especially important when analyzing the different theories for the resurrection of Jesus. It’s also important when evaluating alternative hypotheses that atheists put forward to counter God's existence. 

Let’s go back to our “house-on-fire” example. Let’s say that we know three facts about our situation. First, it smells like smoke, second, my roommate yelled “fire” and third, my door is hot to the touch. What is the best explanation of these three facts? 

First we could say that my roommate simply burnt popcorn, and this accounts for why I smell smoke. However, this theory lacks explanatory power. For example, it doesn’t tell us why my roommate yelled “fire” and why my door is hot to the touch. A theory lacks explanatory power when it doesn’t account for all the facts in question. 

Another theory is that we could claim that my roommate burnt popcorn and that he was doing target practice with a nerf gun. Perhaps, just as he burnt the popcorn, he yelled “ready, aim fire!” Finally, perhaps the door is hot to the touch because he placed a space heater right outside my door, in order to heat the hallway. This theory has good “explanatory power” in that it accounts for all the facts. However, it lacks simplicity. All things being equal, simple theories are better than more complicated one’s. 

Imagine a third situation. Let’s say I’m sitting here evaluating this evidence. And then I come up with a theory. Perhaps as a prank, my landlord entered our house and threw a smoke bomb into the hallway. Perhaps he held a gun to my roommate's head, and ordered him to yell “fire!” very loudly. And to further this horrible prank, perhaps the landlord placed a space heater outside my door, in order to deceive me into thinking the house was on fire. 

This theory is simple, because it only has one cause for the three facts, namely the evil landlord. Furthermore, the theory has great explanatory power, in that it accounts for all the facts. However, the theory has a very important weakness, in that it is very “ad hoc.” This means it is contrived, or it seems made up to explain a certain situation. It involves using assumptions that have no evidence in order to account for all the facts. Namely, we don’t have separate evidence to believe that the landlord invaded the house, in order to pull such a prank. 

Finally, imagine the house on fire. This is a remarkably simple explanation for our three facts. Furthermore, it accounts for all three facts, not just one or two of them. Finally, it is not as ad hoc, in that we don’t have to involve too many assumptions with no evidence to wriggle out of the idea that the house is on fire. 

As we’ve seen, the best theories have at least the following characteristics:

  1. Explanatory power - It accounts for all the facts in question

  2. Simple - The theory is not unnecessarily complicated 

  3. Less ad hoc - The theory doesn't have very many un-evidenced assumptions.

These will play a big role when analyzing some of the arguments for God’s existence, and especially for the resurrection of Jesus. 

For example, let’s start with a few facts that many historians accept. Let’s say that we all agree that there was a guy named Jesus who got crucified by the Romans. Let’s say he died from that, and was placed in a tomb. Now, let’s say that on Sunday morning, that tomb was discovered empty for some reason. Furthermore, his disciples starting running around telling everyone that he was alive. Finally, let's say that Jesus' unbelieving brother, James, converted because he too told people that he saw Jesus after he died.

Now let’s say, to explain these facts, that the disciples of Jesus had hallucinations of him after he died. After all, it's common for people to have bereavement hallucinations after a loved one has died, wherein they see that person again. Perhaps this can explain the facts we just mentioned. Can anyone think of any problems with this?

It’s a simple theory, but it doesn’t explain all the facts. It explains why the disciples saw Jesus after he died, but doesn’t explain why the body is missing from the tomb. It also doesn't explain why James, the skeptic, had a hallucination as well. It lacks explanatory power.

Now let’s say, to explain these facts, that the disciples of Jesus stole the body from the tomb, and then lied about the resurrection of Jesus. Furthermore, the skeptic James had a "guilt hallucination" of his brother after he died. This type of explanation accounts for all the facts. But it is an unnecessarily complicated theory. Any theory that involves a combination of explanations is going to be more complicated, and thus less likely. 

Finally, let’s imagine that Jesus died. But let’s say that he has an evil twin brother, who is in town for Passover. Let’s say that he learns that Jesus has just died. As a result, he goes and steals the body. He then presents himself to Jesus’ disciples and Jesus' skeptical brother James, proclaiming that he had risen from the dead. This accounts for all the facts doesn’t it? Furthermore, it’s a simple theory, because we got one guy who accounts for all the facts, namely, the evil twin brother. However, it’s really ad hoc. It sounds like we made up the idea of an evil twin to get out of the resurrection idea. We don’t actually have any good reason to think that Jesus had a twin, other than wanting to get out of the resurrection idea. 

Then of course, the resurrection is one of the better options. It is simple, accounts for all the facts, and doesn’t involve very many extra assumptions just to account for that fact. 

We will go in depth on this subject when exploring the resurrection of Jesus. But as you can see, understanding abductive reasoning is pretty important for evaluating different theories about the resurrection, or about God’s existence too. 


So far, we’ve seen what it means to have “evidence” for something. We have evidence for a hypothesis when we find out something surprising that wouldn’t be surprising if the hypothesis was true. Evidence is something we would expect if the hypothesis was true, and something we would not expect if the hypothesis were false. 

Furthermore, we have seen three different types of reasoning, inductive, deductive, and abductive. 

Inductive reasoning makes a generalization from a specific observation. For example, all men are mortal. Perhaps there is a man somewhere that is immortal (Jesus after his resurrection is a good example of this!) But as far as we know, every man is mortal. 

Deductive reasoning leads to a conclusion if the supporting statements are true. For example, all men are mortal, Socrates is a man, therefore Socrates is mortal. 

Abductive reasoning involves picking the best theory out of multiple options. We have seen that we should prefer theories which are simple, and account for all the facts. Furthermore, we should discard theories that involve too many assumptions which lack evidence, or one’s that sound like they were made up to avoid some other kind of obvious conclusion. 

Next week, we will talk about the Kalam Cosmological Argument. This is the most discussed argument for God's existence in the philosophical literature in the past few decades.

(All Scripture quotations are from the English Standard Version of the Bible)


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