When I have debates with theists I often ask what evidence there is to convince us there is a god, if the conversation goes on long enough eventually they will bring up bible prophecy that predicts events before they happen as clear proof that a god exists. I happened to run into such a person just today
In my estimation prophecy would need to be able to do two things to prove, within reason, that it is actually foretelling the future.
First it ought to be specific. For instance, say I told you my psychic abilities gave me the ability to predict the winning lottery number. However, when you asked for proof I produced a spreadsheet that listed every possible derivation of numbers that could possibly appear in said lottery and said the winning number is one of these. I would technically be right, but only in the sense that my prediction was so general that it could not possibly be wrong. Not only does this not demonstrate supernatural abilities, it not going to improve your chances of winning the lottery. So predictions that are too general are out because it is too easy to get things right without actually knowing anything about the future. We see examples of this in action all the time with psychics who “predict” banal things like earth quakes. They could fix this by giving us the exact time, and location of the earthquake, but they won’t because they don’t want to make a claim that is falsifiable.
Secondly the source of the predictions needs to be consistent. That is, it should be able to make many predictions all, or at least most, of which turn out correct. This is because of a little thing called statistical inevitability. That is to say even if the chance of something happening is very low, if you produce the circumstances in which the event can occur enough times eventually it becomes likely that it will have happened in at least one of those instances. To put it another way, if I make hundreds of thousands of predictions, even very specific ones, eventually one of them will turn out right even without actual prophetic powers. Further, given this, even if I make only one prediction that turns out to be right, it is still probably more likely that I got lucky than I’m actually a prophet. So we need multiple data points to build a case that something significant is going on.
So the key is to make detailed prophecies of future events that almost always turned out to be highly accurate. So before we delve into the bible to see if it holds up lets look at a non-biblical prophecy to see how these standards work.
A quick Google search turned up a webpage that speaks favorably about Nostradamus’ predictions
Here is a quote from Nostradamus that his devotees regularly quote as being a prediction of nuclear weapons:
"Near the gates and within two cities
There will be scourges the like of which was never seen,
Famine within plague, people put out by steel,
Crying to the great immortal God for relief."
So is this claim exact? It mentions two cities but does not tell us the name of those cities, it does not tell us anything about the date that this might occur, it does not mention nuclear bombs, atoms, or even explosions for that matter. It is all very vague. One could argue that saying two cities is specific, but with all of the events out there in the world if he had said 3 cities or 10 people could have easily attached this to some other event. How does the website deal with the passage?
This one is hard to dispute... It's an accurate depiction of the nukes being used on Hiroshima and Nagasaki. "Scourges the like of which was never seen," and people "crying to the great immortal God." Of course it's vague - and you could insert other events that have effected 2 populaces - but in our known history, the dropping of atomic weapons on Japan is a huge turning point in our history, warfare, and politics.
He claims it’s an accurate description of nuclear weapons being used at the end of WWII but his reasoning is completely ad hoc. There is no way you would look at this passage and know what was going to happen before it happened. He clearly just finds an event in history that looks vaguely like the description and then shoe horns it in to the passage. As far as the second rule, Nostradamus does make a lot of predictions, but unfortunately for him they are all about as clear as this one.
Now, lets move on to the Bible, I’m not going to look at the whole thing because that would be much longer post so we will suffice for now to look at a fairly famous examples of prophecy in the bible.
Isaiah 7:14 is one of the passages that is famous for supposedly predicting the birth of Jesus.
7:14 Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel. 7:15 Butter and honey shall he eat, that he may know to refuse the evil, and choose the good.
It is, of course, important to note that there is reason to suspect that the use of the word virgin in verse 14 is incorrect. The Hebrew word translated here refers to a young woman but not necessarily to her sexual status. The confusion there was originally caused by a mistranslation in the Septuagint which was the source for the original KJV bible.
Next, the passage isn’t quite a vague as Nostradamus, but it still leaves a lot to be desired. No dates or times listed. It says a woman will conceive, but does not name her and a woman having a child is not particularly out of the ordinary, especially in a world sans reliable birth control.
Jesus was of course never called Immanuel in the gospels but most Christians say that was meant to be metaphorical since Immanuel means “god with us.” Still it stretches credulity, prophecy always seems to be filled with statements that people decide should be read metaphorically after the fact. If they were clear as I suggest then we wouldn’t have these issues to sort out. In addition, some of the details it does give are not only fairly useless, but also make no logical sense. It says he will eat butter and honey so he will that he may know to refuse evil. How exactly does eating any kind of food help one refuse evil? This is not only vague it doesn’t even make any sense.
Further, if you read the wider context of this section by going back to the beginning of the chapter, is not even attempting a prophecy of for Jesus. It is clearly speaking about a war with Syria.
7:1 And it came to pass in the days of Ahaz the son of Jotham, the son of Uzziah, king of Judah, that Rezin the king of Syria, and Pekah the son of Remaliah, king of Israel, went up toward Jerusalem to war against it, but could not prevail against it.
Then the king hears that Syria is allies with Ephraim, so Isaiah goes to speak to Ahaz and to tell him to not be worried because they won’t win and Ephraim will be destroyed within five years. So God speaks to Ahaz and offers to give him a sign as proof that they will be protected in the coming war. This child's birth is offered as such a sign. So not only is the passage a weird and vague failure of a prophecy it never even attempted to be the prophecy Christians want it to be. This is not an isolated passage either, one can find the same kinds of flimsy “prophecy” littering the bible.
I want to go one step further than this though. For the sake of argument let us assume a reality where these passages did live up the standards I posed above. The prophecies were both incredibly detailed and consistently right. Christians present this best case scenario as definitive proof of a god, but, in fact, it is not. The only thing that this scenario actually proves is that the person who wrote it knew things about the future that he should not have been able to know given our current understanding of how the universe works.
Certainly god could be a possible explanation for this scenario, but then so could time travel or psychic abilities. Sure there is no evidence for those, but neither is there any evidence for god outside of the aforementioned prophecies. Of course the theist might point out at this point that if the person giving the prophecy claimed that god was the source of his revelation that would lend credence to the god hypothesis, but this is a fairly weak argument. He could be lying, he may believe god has given him the revelation, but be mistaken, or the actual source of the information could intentionally deceiving him. Admittedly these scenarios are unlikely, but then without some further evidence beyond the prophecy itself God is also an unlikely explanation. In this way, prophecy is a very weak argument for the existence of god.
Now that this has been explained I’m sure theists will stop using this as an argument now. Right?…