The logic of cause and effect

We live in a cause-and-effect universe. Every effect has a cause. It is common sense. And the scientific method is based on cause and effect. Logic is the study of correct and incorrect reasoning (Appendix A)

If A causes (or implies) B, then A is the cause or antecedent and B is the effect or consequent. This means that A is necessary for B. It can also be referred to as a conditional statement, “if A, then B”.

For example:
A: Jesus rose from the dead (cause)
B: His bones cannot be found (effect)

Correct reasoning

The following can be inferred from the relationship that A causes (or implies) B. If A is true, then B is true. This is called affirming the antecedent (or cause). On other hand, if B is false, then A is false. This is called denying the consequent (or effect).

For example, affirming the antecedent (or cause):
– If Jesus rose from the dead.
– Therefore, His bones cannot be found.
This is valid reasoning. So if the premises (A and B) are true, so is the conclusion.

Conversely, denying the consequent (or effect):
– If Jesus’ bones can be found.
– Therefore, Jesus did not rise from the dead.
This is valid reasoning, despite the fact that both premises are false. Therefore, the conclusion is false.

For the conclusion to be true, both the premises must be true and the reasoning must be valid. But the validity of the reasoning is independent of the truth or falsity of the premises or conclusion.

There are other examples of correct reasoning in Appendix B.

Incorrect reasoning

The following are invalid inferences from the relationship that A causes (or implies) B. If B is true, then A is true. This is called the fallacy of affirming the consequent (or effect). This is a fallacy because it assumes that the conclusion could only have been reached in one particular way. It jumps to conclusions without considering other possible causes of the effect. Likewise, if A is false, then B is false. This is called the fallacy of denying the antecedent (or cause).

For example, the fallacy of affirming the consequent (or effect):
– If Jesus’ bones cannot be found.
– Therefore, Jesus rose from the dead.
This is invalid reasoning because a dead person’s bones may have been cremated. We cannot validly claim that an antecedent of a conditional statement is true by arguing that the consequent is true (except in the case of an “if and only if” statement).

Conversely, the fallacy of denying the antecedent (or cause):
– If Jesus did not rise from the dead.
– Therefore, His bones can be found.
This is invalid reasoning. Many people who did not rise were cremated. We cannot validly claim that a consequent of a conditional statement is false by arguing that the antecedent is false.

There are other examples of incorrect reasoning in Appendix C.

Christianity

The Bible asserts the cause-effect relationship, “Don’t be misled—you cannot mock the justice of God. You will always harvest what you plant. Those who live only to satisfy their own sinful nature will harvest decay and death from that sinful nature. But those who live to please the Spirit will harvest everlasting life from the Spirit” (Gal. 6:7-8NLT).

Some people reverse cause and effect with regard to the Bible. For example it has been claimed that, “The Bible’s account of the Genesis flood borrows from earlier myths. Over 270 cultures have flood myths, and they are surprisingly similar in many details”. Actually, it’s the other way around. It would be expected that such a momentous event would be remembered by many cultures.

The Kalam Principle says that whatever begins to exist has a cause; the universe began to exist; so the universe has a cause. The cause of time, space, energy, and matter is the eternal God.

A: (If and only if) I trust in Christ.
B: I have many spiritual blessings (from the God who created the universe; Eph. 1:3).

Affirming the antecedent (or cause):
– If I trust in Christ.
– Therefore, I have many spiritual blessings.
This is valid reasoning. So, if the premises (A and B) are true, so is the conclusion.

Denying the consequent (or effect):
– If I don’t have many spiritual blessings.
– Therefore, I don’t trust in Christ.
This is valid reasoning. So, if the premises (A and B) are true, so is the conclusion.

In this case, affirming the consequent (or effect) is valid:
– If I have many blessings.
– Therefore, I trust in Christ.
This is valid reasoning because of the “if and only if” statement. There is no other way to receive lasting spiritual blessings.

Fallacy of denying the antecedent (or cause):
– If I do not trust in Christ.
– Therefore, I don’t have many blessings.
This is valid reasoning because of the “if and only if” statement. There is no other way to receive lasting spiritual blessings.

Lessons for us

The Bible teaches that God is the ultimate cause for the existence of the universe. And the global flood in the Bible is the antecedent of the flood myths in other cultures.

Let’s use correct logic in our conversations. For example, except for an “if and only if” statement, affirming the consequent is a logical fallacy.

Appendix A: Logic

“Logic is the science of the relations between propositions. Logic can tell us what can be inferred from a given proposition, but it cannot tell us whether the given proposition is true in the first place. All philosophical systems rely on logical deductions from starting assumptions—axioms—which, by definition, cannot be proven from prior assumption. For our axioms, it is rational to accept the propositions revealed by the infallible God in the 66 books of the Bible” (Sarfati, 1998).

Appendix B: Other examples of correct reasoning

A: It is raining.
B: The grass is wet.

Affirming the antecedent (or cause):
– It is raining.
– Therefore, the grass is wet.
This is valid reasoning.

A: I ran out of fuel.
B: My car engine would stop.

Denying the consequent (or effect):
– If my car engine has not stopped.
– Therefore, I cannot have run out of fuel.
This is valid reasoning.

A: I am a human.
B: I am warm-blooded.

Denying the consequent (or effect):
– I am not warm-blooded.
– Therefore, I am not human.
This is valid reasoning.

A: Animals are descended from a common ancestor.
B: Their embryonic development is expected to be similar.

Denying the consequent (or effect):
– If animals embryonic development is not similar.
– Therefore, they are not descended from a common ancestor.
This is valid reasoning.

A: God does not exist.
B: Objective moral values and duties do not exist.

Denying the consequent (or effect):
– If objective moral values and duties exist.
– Therefore, God exists.
This is valid reasoning.

Appendix C: Other examples of incorrect reasoning

A: It’s raining.
B: The streets are wet.

Fallacy of affirming the consequent (or effect):
– If the streets are wet.
– Therefore, it’s raining.
This is invalid reasoning as there are many other reasons why the streets could be wet.

A: I ran out of fuel.
B: My car engine would stop.

Fallacy of affirming the consequent (or effect):
– If my car engine has stopped.
– Therefore, I must have run out of fuel.
This is invalid reasoning as there are many other reasons why a car engine would stop.

A: Someone is human.
B: They are mortal.

Fallacy of affirming the consequent (or effect):
– If someone is mortal.
– Therefore, they are human.
This is invalid reasoning because someone could be a dog.

A: Evolution is true.
B: Many organisms have similarities.

Fallacy of affirming the consequent (or effect):
– If we see many organisms with similarities.
– Therefore, evolution is true.
This is invalid reasoning as there could be other reasons why many organisms have similarities.

A: Evolution is true.
B: There are similarities in the DNA of all organisms on earth.

Fallacy of affirming the consequent (or effect):
– If we see similarities in the DNA of all organisms on earth.
– Therefore, evolution is true.
This is invalid reasoning as creationists would also expect to see similarities in the DNA of all organisms, since the original kinds were made by the same Creator.

A: The big bang is true.
B: We expect to see a cosmic microwave background.

Fallacy of affirming the consequent (or effect):
– If we see a cosmic microwave background.
– Therefore, the big bang is true.
This is invalid reasoning as it fails to consider other possible causes for the cosmic microwave background.

A: God created the universe.
B: The universe is orderly and obeys natural laws.

Fallacy of affirming the consequent (or effect):
– If the universe is orderly and obeys natural laws.
– Therefore, God created the universe.
This is invalid reasoning because the order and the laws could have another cause. This is a logical possibility.

A: I am a Christian.
B: I do good works.

Fallacy of affirming the consequent (or effect):
– If I do good works.
– Therefore, I am a Christian.
This is invalid reasoning because being a Christian is not the only explanation for doing good works.

A: I am a follower of Jesus Christ.
B: I am hated by unbelievers (Jn. 15:18-25).

Fallacy of affirming the consequent (or effect):
– If I am hated by unbelievers.
– Therefore, I am a follower of Jesus Christ.
This is invalid reasoning because being a Christian is not the only explanation for being hated by unbelievers.

A: There was a global flood.
B: There are lots of fossils.

Fallacy of affirming the consequent (or effect):
– If there are lots of fossils.
– Therefore, there was a global flood.
This is invalid reasoning because there might be another reason for lots of fossils. This doesn’t mean that there was no global flood, just that it can’t be proven by this logic.

By the way, affirming the consequent is valid if the first premise asserts “if and only if” rather than “if”.

A: It’s snowing.
B: It’s cold outside.

Fallacy of denying the antecedent (or cause):
– If it’s not snowing.
– Therefore, it’s not cold outside.
This is invalid reasoning as it could be cold outside and still not snow.

A: It’s barking.
B: It’s a dog.

Fallacy of denying the antecedent (or cause):
– If it’s not barking.
– Therefore, it’s not a dog.
This is invalid reasoning because it doesn’t say that every dog barks.

A: God exists.
B: People have moral obligations.

Fallacy of denying the antecedent (or cause):
– If God doesn’t exist.
– Therefore, people do not have moral obligations.
This is invalid reasoning.

A: God could speak to me audibly.
B: Then I would know God exists.

Fallacy of denying the antecedent (or cause):
– If God doesn’t speak to me audibly.
– Therefore, God does not exist.
This is invalid reasoning

References

Dare T, 2022, “How to argue against common fallacies”, University of Auckland.

Lisle J, 2009, “Formal fallacies – Affirming the Consequent and Denying the Antecedent”.

Sarfati J, 1998, “Loving God with all your mind: logic and creation”, J of Creation, 12(2):142–15.

Statham D, 2021, The wonder of science – Exploring the creation/evolution debate”, Creation Book Publishers, 44.

Written, September 2022