There is no RationalWiki without you. We are a small non-profit with no staff – we are hundreds of volunteers who document pseudoscience and crankery around the world every day. We will never allow ads because we must remain independent. We cannot rely on big donors with corresponding big agendas. We are not the largest website around, but we believe we play an important role in defending truth and objectivity. If everyone who saw this today donated $5, we would meet our goal for 2021. |
Fighting pseudoscience isn't free. We are 100% user-supported! Help and donate $5, $20 or whatever you can today with ! |
Essay:Why the "fine-tuned universe" argument is bogus
Creationists use the fine-tuned universe argument as evidence for God's existence. Life (or the formation of stars, depending on the source) presupposes a narrow range of physical constant, and any universe with alternate constants does not support life. Because there are many possibilities outside this range of values, life must be astronomically improbable, and the universe we are in must not have formed by chance. Therefore, God (or another supernatural agent) must have had a role in the formation of the universe.
In this essay, I will show that this fine-tuned argument is bogus for two reasons: (1) The improbability of the universe it pretends to assess is either unknown or irrelevant and (2) there is no relationship to the God's existence. To show this, we will use an example of your dog in your car.
The dog in the car example[edit]
Suppose you leave your car in a crowded parking lot. The errand you are running will only take a minute, so you leave your dog in your locked, closed-up car. (You should never do this, of course; don't try this at home.) Upon returning, you cannot find your car, but after looking around for a bit, you see your dog in a car.
Being mathematically minded, you consider the following probabilities.
1. What is the probability that the car that your dog is in is yours?
- This is obvious. Barring a magical event, the probability that your dog is in your car is 100%. This is equivalent to saying that the conditional probability that the car is yours given that your dog is in it is 100%.
2. What is the probability that your dog is in a car?
- This, again, is obvious. Since you observe that your dog is in a car, this probability is 100%. Hence, the conditional probability that your dog is in any car given that you observe your dog is 100%.
3. What is the probability that you find your dog upon randomly looking in a car?
- This depends on the number of cars, and the probability is 1/n, with n equal to the number of cars. However, this number is uninteresting and largely irrelevant. Because you already know where your dog is, thinking back to when you were searching for the dog is not particularly interesting. You already know that the dog is in the car, and hence it is a given when considering new probability in the future. In addition, to get a number, one would need to know the number of cars, which is unknown.
The corresponding elements in the fine-tuned universe argument are as follows: (1) life corresponds to the dog; (2) the current, supposedly "fine-tuned" universe corresponds to your car; and (3) other, hypothetical universes correspond to the other cars in the parking lot.
The corresponding probabilities to consider are as follows:
1. What is the probability that life exists in our present universe?
- As you pinch yourself, this is obvious: 100%. The conditional probability of being in our (supposedly "fine-tuned") universe is 100%.
2. What is the probability that life exists in one of all possible universes?
- Pinching yourself and looking around, this is again 100%.
3. What is the probability when considering hypothetical universes with alternate physical constants that life exists in a randomly considered universe?
- Like above, this depends on the number of universes. However, also like above it is irrelevant. Because you already know that our universe has life in it, considering hypothetical universes provides no additional interesting information because you know that you are in your universe and you know that life exists. All future considered probabilities consider this knowledge. Most people confuse the probability considered in point 2 with that in point 3.
To assess the probability that life exists, you would need to know the number of viable universes, which is unknown. We cannot observe these universes, nor can we look for one that does not contain life. In reality, the probability that life exists would also depend on the probability that such universes exist, a complication not addressed in the dog in the car example. After all, life should not become any less probable because you considered more universes that are hypothetical.
That a narrow range of physical constants can support is also irrelevant, as consideration of any hypothetical universe no matter how it is defined does not change your current knowledge of the universe.
What about God?[edit]
Nowhere in any of the discussion is the probability that God exists considered. The creationists assume that if an event is improbable, Goddidit. Any event that is less probable than an arbitrary number is deemed, "by chance" and hence. Yet there is no reason why this is valid.
It is also unclear that the universe forming from naturalistic processes sampled alternate universes and randomly settled on the current one. In many ways, the universe just is.
See also[edit]
Any source on the prosecutor's fallacy, such as this one.