A Method for Evaluating the Strength of Causal Claims

An elementary school student might think to himself something like the following,

"When scientists figure out the cause of some effect, they start saying that such a cause is the reason why the effect occurs. If they don't know what causes the effect, they just say they don't understand what causes it."

Such a generalization is naive. A more accurate and realistic description is the one below:

Scientists often determine the cause of an effect, and begin to state that cause as the reason why that effect occurs. In many other cases, humans are unable to figure out what the cause of an effect is. But that doesn't stop scientists from making claims about what causes the effect. In many cases such claims are weakly supported by evidence or logic, but scientists continue to make such claims because the assertion of such claims has become a speech custom of scientists, or because the claims help the scientists avoid or sweep under the rug some possibility they prefer not to believe in.

Given such a situation, it is helpful to have some method for evaluating the strength of causal claims. Using such a system, we might be able to distinguish between strong causal claims and weak causal claims. I can think of such a method, which I list below.

In the method I propose, we ask many different questions, and either add or subtract points based on the answers. Here are the questions:

Y= Effect, X=proposed cause of the effect
1. Has Y always been observed occurring whenever X occurs?	+1
2. Has Y usually been observed occurring when X occurs?	+1
3. Has Y sometimes been observed occurring when X occurs?	+1
4. Has Y never been observed occurring when X occurs?	-1
5. Does X usually occur without producing Y?	-1
6. Does X sometimes occur without producing Y?	-1
7. Does Y always occur very close in time and space to X?	+1
8. Can we think of some reason why X would always produce Y?	+1
9. Can we think of some reason why X would usually produce Y?	+1
10. Can we think of some reason why X would occasionally produce Y?	+1
11. Can we think of some reason why X would never produce Y?	-1
12. Can we think of some reason why X would usually not produce Y?	-1
13. Are there no other reasonable theories of how Y could be produced other than assuming X produced it?	+1
14. Can we think of a fact or facts that are true, but which are surprising or unexpected if X causes Y?	-1
15. Can we think of some fact or facts that are true, but hard to explain unless X causes Y?	+1
16.  If X an undisputed reality that has been instrumentally measured or photographed?	+1

Using this system, we should find that strong causal claims end up with a positive score, and weak causal claims end up with a zero or negative score. The stronger the causal claim, the higher the should be, and the weaker the causal claim, the lower the score should be.

Let's try this system, using a specific example. An example of a causal claim is the claim that water freezing is caused by temperatures below 0 degrees Celsius. Below is how we can compute the score of this causal claim. (For the purpose of simplicity, the only places being considered are the surface of Earth and the surface of the moon.) 

Y= Water freezing, X=Temperatures below 0 degrees Celsius
1. Has Y always been observed occurring whenever X occurs?	0	An arid landscape (such as on the moon) can show no signs of water freezing even when temperatures are below 0 degrees Celsius.
2. Has Y usually been observed occurring when X occurs?	+1	We usually observe freezing at temperatures below 0 degrees Celsius.
3. Has Y sometimes been observed occurring when X occurs?	+1	We usually observe freezing at temperatures below 0 degrees Celsius.
4. Has Y never been observed occurring when X occurs?	0	Water has been observed freezing at emperatures below 0 degrees Celsius.
5. Does X usually occur without producing Y?	0	Temperatures below 0 degrees Celsius usually do not occur without producing water freezing
6. Does X sometimes occur without producing Y?	-1	Temperatures below 0 degrees Celsius sometimes occur without producing water freezing, in arid places like the moon.
7. Does Y always occur very close in time and space to X?	+1	Water freezing always occurs at the same time and place as temperatures below 0 degrees Celsius.
8. Can we think of some reason why X would always produce Y?	0	We can think of no reason why temperatures below 0 degrees Celsius would always cause water freezing, because on some landscapes like the moon there is no water.
9. Can we think of some reason why X would usually produce Y?	+1	We can think of a reason why temperatures below 0 degrees Celsius would usually cause water freezing, given that most places have water that might freeze.
10. Can we think of some reason why X would occasionally produce Y?	+1	We can think of a reason why temperatures below 0 degrees Celsius would sometimes cause water freezing, because most places have water that might freeze.
11. Can we think of some reason why X would never produce Y?	0	There is no reason why temperatures below 0 degrees Celsius should never produce water freezing.
12. Can we think of some reason why X would usually not produce Y?	0	Given that most places have water, there is no reason why temperatures below 0 degrees Celsius should usually not produce water freezing.
13. Are there no other reasonable theories of how Y could be produced other than assuming X produced it?	+1	No one has advanced an alternate theory of how water freezing could occur other than temperatures below 0 degrees Celsius.
14. Can we think of a fact or facts that are true, but which are surprising or unexpected if X causes Y?	0	No, we can't.
15. Can we think of some fact or facts that are true, but hard to explain unless X causes Y?	+1	Frozen water (ice) is very cold, and we would not expect it to be so cold unless temperatures below 0 degrees Celsius had caused it get so cold.
16.  If X an undisputed reality that has been instrumentally measured or photographed?	+1	No one disputes that there are temperatures below 0, and such temperatures have been instrumentally  measured with a thermometer.

So using this scoring system and adding up all the numbers, it turns out that the claim that water freezing is caused by temperatures below 0 degrees Celsius ends up with a score of +7. In this case, the system seems to work well. We have a very strong cause and effect relation in this case, and the causal explanation has scored highly using our system.

Let's try this system, using another specific example. An example of a causal claim is the claim that thunder is caused by lightning. Below is how we can compute the score of this causal claim.

Y= Thunder, X=Lightning
1. Has Y always been observed occurring whenever X occurs?	0	While thunder is believed to occur whenever lightning occurs, we sometimes hear no thunder when we see lightning.
2. Has Y usually been observed occurring when X occurs?	+1	We usually do hear thunder when lightning occurs.
3. Has Y sometimes been observed occurring when X occurs?	+1	We usually do hear thunder when lightning occurs.
4. Has Y never been observed occurring when X occurs?	0	Thunder does occur when lightning occurs.
5. Does X usually occur without producing Y?	0	Visible lighting usually produces audible thunder.
6. Does X sometimes occur without producing Y?	0	It is believed that lightning always produces thunder, even when we fail to notice the thunder.
7. Does Y always occur very close in time and space to X?	+1	Thunder is thought to always occur at the same time and place as lightning.
8. Can we think of some reason why X would always produce Y?	+1	There are scientific reasons why lightning should always produce thunder.
9. Can we think of some reason why X would usually produce Y?	+1	There are scientific reasons why lightning should always produce thunder.
10. Can we think of some reason why X would occasionally produce Y?	+1	There are scientific reasons why lightning should always produce thunder.
11. Can we think of some reason why X would never produce Y?	0	No.
12. Can we think of some reason why X would usually not produce Y?	0	No.
13. Are there no other reasonable theories of how Y could be produced other than assuming X produced it?	0	There is the theory that thunder is a roar of angry gods or spirits.
14. Can we think of a fact or facts that are true, but which are surprising or unexpected if X causes Y?	0	No, we can't.
15. Can we think of some fact or facts that are true, but hard to explain unless X causes Y?	0	There may well be, but I can't think of any.
16.  If X an undisputed reality that has been instrumentally  measured or photographed?	+1	No one disputes that lightning exists, and it has been photographed.

So using this scoring system and adding up all the numbers, it turns out that the claim that thunder is caused by lightning ends up with a score of +7. In this case, the system seems to work well. We have a very clear cause and effect relation in this case, and the causal explanation has scored highly using the method I have proposed for judging the strength of a causal effect.

Thunder is actually produced by lightning

Now let us consider the claim that complex visible biological innovations are caused by random mutations and what biologists call "natural selection" (a term that is not literally accurate because blind unconscious nature does not literally select things).  By "complex visible biological innovations" I refer only to things appearing in nature, not anything produced artificially by humans, and I refer only to things involving a high level of complexity (not mere superficial changes such as darkening).  Below is how we can compute the score of the causal claim that complex visible biological innovations are caused by random mutations and natural selection.

Y= The appearance of complex visible biological innovations, X = random mutations and natural selection
1. Has Y always been observed occurring whenever X occurs?	0	Humans have not actually observed any complex visible biological innovations appearing. All such innovations appeared before 3000 B.C.
2. Has Y usually been observed occurring when X occurs?	0	Humans have not actually observed any complex visible biological innovations appearing.
3. Has Y sometimes been observed occurring when X occurs?	0	Humans have not actually observed any complex visible biological innovations appearing.
4. Has Y never been observed occurring when X occurs?	-1	Humans have never observed any complex visible biological innovations appearing.
5. Does X usually occur without producing Y?	-1	Scientists say that natural selection is constantly occurring, and that random mutations are constantly occurring. But still humans have never observed any complex visible biological innovations occurring.
6. Does X sometimes occur without producing Y?	-1	Scientists say that natural selection is constantly occurring, and that random mutations are constantly occurring. But still humans have never observed any complex visible biological innovations occurring.
7. Does Y always occur very close in time and space to X?	+1	Although we have not observed complex visible biological innovations occurring, it is claimed that random mutations and natural selection have always been occurring, so we can generously grant that when previous complex visible biological innovations occurred, they were close in time in space to random mutation and some type of survival of the fittest that might be metaphorically called "natural selection."
8. Can we think of some reason why X would always produce Y?	-1	We can think of no reason why random mutations and natural selection would always produce complex visible biological innovations, and scientists think that in most years they do not produce such a thing.
9. Can we think of some reason why X would usually produce Y?	-1	We can think of no reason why random mutations and natural selection would usually produce complex visible biological innovations, and scientists think that in most years they do not produce such a thing.
10. Can we think of some reason why X would occasionally produce Y?	-1	We can think of no reason why random mutations and natural selection would occasionally produce complex visible biological innovations, just as we can think of no reason why tornadoes passing through a city (which produce random effects and a kind of architectural "survival of the fittest") would occasionally produce complex new architectural innovations.
11. Can we think of some reason why X would never produce Y?	-1	We can think of several  reasons why random mutations and natural selection would never produce complex visible biological innovations: (1) the fact that such complex visible biological  innovations require such extremely high states of organization  and fine-tuning that it seems impossible that they would ever be produced accidentally, just as houses of cards should never be formed by throwing a deck of cards into the air, and just as log cabins should never form from falling trees; (2) the fact that individual random mutations (point mutations) are merely tiny fragments of what is needed for a complex visible biological innovation, typically less than 1%; (3) the fact that natural selection (or a superior reproduction rate) never works in regard to some complex biological innovation until such an innovation has already appeared.
12. Can we think of some reason why X would usually not produce Y?	-1	Same as above.
13. Are there no other reasonable theories of how Y could be produced other than assuming X produced it?	-1	There are three other reasonable theories of how complex visible biological innovations might have happened (1) they might have been introduced by a divine creator; (2) they might have been introduced by extraterrestrial visitors wanting for Earth to eventually produce intelligent life; (3) they might have been produced by some cosmic life-force.
14. Can we think of a fact or facts that are true, but which are surprising or unexpected if X causes Y?	-1	The Cambrian Explosion in which most animal phyla originated rather suddenly is unexpected under the theory that complex visible biological innovations are produced by random mutations and natural selection, which have always been described as very slow and gradual effects.
15. Can we think of some fact or facts that are true, but hard to explain unless X causes Y?	+1	There probably are no such facts, given a wide variety of alternative possibilities, but let's grant this +1 point just to be charitable.
16.  If X an undisputed reality that has been instrumentally  measured or photographed?	0	"Natural selection" is disputed as a literally accurate term, on the grounds that only conscious agents select things.  The main idea behind natural selection (that fit things reproduce more) has been disputed, on the grounds that it is unproven (for example, not-very-fit bacteria seem to reproduce at a much higher rate than mammals).  Natural selection has never been instrumentally measured or photographed.

Shockingly, the theory that random mutations and natural selection produce complex visible biological innovations produces a score of only -8, which is 15 points lower than the score produced by the claim that lightning produces thunder and the claim that temperatures of 0 degrees Celsius or lower produce freezing.  This very low score suggests that the theory that random mutations and natural selection produce complex visible biological innovations is far from being a strong causal claim. 

Could it be that something is wrong with my method for evaluating the strength of causal claims? Let's try it again, testing it with the claim that accidental falls from high altitudes produce fatal injuries. 

Y= Fatal injuries, X= accidental falls from high altitudes
1. Has Y always been observed occurring whenever X occurs?	0	Occasionally someone will survive an accidental fall from a high altitude.
2. Has Y usually been observed occurring when X occurs?	+1	Most people who accidentally fall from high altitudes have fatal injuries.
3. Has Y sometimes been observed occurring when X occurs?	+1	Most people who accidentally fall from high altitudes have fatal injuries.
4. Has Y never been observed occurring when X occurs?	0	Most people who accidentally fall from high altitudes have fatal injuries.
5. Does X usually occur without producing Y?	0	Most people who accidentally fall from high altitudes have fatal injuries.
6. Does X sometimes occur without producing Y?	-1	Sometimes people accidentally fall from high altitudes without having fatal injuries.
7. Does Y always occur very close in time and space to X?	-1	Fatal injuries can occur without falling, such as in auto collisions.
8. Can we think of some reason why X would always produce Y?	0	A person accidentally falling from a high altitude may land in a soft surface like a haystack.
9. Can we think of some reason why X would usually produce Y?	+1	Given the acceleration produced by accidental falls from high altitudes, we can think of a reason why they would usually produce fatal injuries.
10. Can we think of some reason why X would occasionally produce Y?	+1	Given the acceleration produced by accidental falls from high altitudes, we can think of a reason why they would usually produce fatal injuries.
11. Can we think of some reason why X would never produce Y?	0	No.
12. Can we think of some reason why X would usually not produce Y?	0	No.
13. Are there no other reasonable theories of how Y could be produced other than assuming X produced it?	0	Fatal injuries can be produced by car crashes that do not involve falls from high altitudes.
14. Can we think of a fact or facts that are true, but which are surprising or unexpected if X causes Y?	0	No, we can't.
15. Can we think of some fact or facts that are true, but hard to explain unless X causes Y?	0	No, we can't.
16.  If X an undisputed reality that has been instrumentally measured or photographed?	1	No one disputes there are accidental falls from high altitudes, and they  have been photographed.

So according to this system, the overall strength of the claim that accidental falls from high altitudes produce fatal injuries is +3. While not as strong as the +7 scores reached by the theory that lightning causes thunder and the theory that temperatures below 0 degrees Celsius produce freezing, at least the scoring system has given a positive score to a strong causal claim.  So it seems that the method I have suggested here works well in distinguishing between causal claims that are weak and those that are strong. 

So why is it that we continue to have so many assertions of the claim that complex visible biological innovations are caused by random mutations and natural selection, despite the weakness of such a causal claim? It would seem the answer is: largely because this is a speech custom that is imposed by institutional powers that compel or prod people to say a particular thing.

We might also ask: why do millions of children in school state every day the false claim that there is "liberty and justice for all" in America? It is a fine thing for school children to "pledge allegiance to the flag, and to the republic for which it stands." But a BBC article tells us, "Prison rates in the US are the world's highest, at 724 people per 100,000." Very many of these people in prison should not be there, and are there because the people could not afford good lawyers, were imprisoned because of over-zealous drug laws, or were the victims of racial prejudice. Meanwhile many people who commited the worst kind of crimes between 2003 and 2009 suffered no legal penalties at all, because they were rich enough to afford skillful lawyers or politically protected.  So it seems that while in the United States there is liberty and justice for most, there is neither "liberty for all" nor "justice for all."  So why is it that millions of children every school day assert the false claim that in America there is "liberty and justice for all"? The answer is:  because this is a speech custom that is imposed by institutional powers that compel or prod people to say a particular thing.