This is when we illegitimately appeal to ignorance to support a conclusion. It usually takes the following form: “No one has proven not A, therefore A is true.” It may also take this form: “No one has proven A, so A is false.”
Notice this fallacy is not about an ignorant person; rather it is when we mistakenly believe that something must be false because it has not been proven true, or that something must be true because it has not been proven false.
1) You cannot prove God does not exist, therefore God exists.
2) You cannot prove God exists, so God does not exist.
3) You cannot prove vegetables are not sentient, so we should treat them as if they are sentient.
4) You cannot prove invisible fairies do not live in my nose; therefore they live in my nose.
5) You cannot prove that we will not create strong artificial intelligence in the future, therefore we will.
6) You cannot prove time travel won't be possible in the future, therefore it will be possible.
The point of this fallacy is a claim is not true simply because we cannot prove it false. Also, a claim is not false simply because we cannot prove it true. We cannot usually move from our ignorance (i.e. not knowing) to claims about reality.
However, it is sometimes permissible to argue from ignorance. For example, our court system mandates that a person is innocent until proven guilty. If the prosecution cannot prove he is guilty beyond a reasonable doubt, the jury must conclude his innocence and acquit. In the courtroom, it is permissible to argue, “You cannot prove he is not innocent, so he is innocent.”
Another exception to the argument from ignorance fallacy arises when we test very specific claims. For example, imagine I claim there are three orange trees growing in my backyard. Let’s say you visit my backyard, but do not see any trees. In this case, the absence of evidence is evidence of absence. That is, my inability to show you the orange trees is good evidence for there not being orange trees. It is permissible for you to argue, “You cannot prove there are orange trees in this yard, so there are not any.” So, it is sometimes permissible to argue “You cannot prove A exists, so A does not exist.” In short, it is not a fallacy if there should be evidence in this case, but we do not find it after seriously looking.
The fallacy of misplacing the burden of proof is closely related and arises “when people are misled into thinking they have to disprove a claim, when their opponent should be proving his claim” (Parker & Moore, 2009). Determining who has the burden of proof can be complex, and the burden of proof usually shifts back and forth during debate.
For example, the person making a positive assertion usually has the burden of proof (e.g. the theist who asserts God’s existence). Once the theist presents an argument for God’s existence, the burden of proof is now on the atheist who denies God’s existence. Once the atheist shows what is wrong with the argument or presents a new argument against God’s existence, some or all of the burden shifts back to the theist. And so it continues.
Philosophy of Religion is the field of study that thoroughly and systematically studies the arguments on both sides. Most theists and atheists have poorly reasoned opinions because they have not studied these works; they are not standing on the shoulders of the giants who preceded them.
A digression: If there were a God, why should we expect to know it through physics or the other sciences? Perhaps poetry, art, and metaphor are the only ways to know such a “being”? Is belief in God like belief in orange trees? Can the atheist infer God does not exist simply because there is a lack of empirical evidence? How can the theist detect purpose if purpose is not empirical? Is arguing against God’s existence like arguing against the existence of orange trees in my backyard? Philosophy of Religion is fascinating. As a sidenote, I believe the strongest argument against God’s existence is a logical argument (the evidential argument from evil). And I believe the strongest argument for God’s existence is religious or mystical experience.
How to avoid
Be skeptical whenever someone attempts to prove a claim by using your inability to disprove one. Be skeptical when people use a lack of understanding (i.e. ignorance) to make a claim about reality. Be suspicious whenever someone says, “Well, you cannot prove it is not true!”
- Discuss the problems with the following arguments.
You cannot prove aliens do not exist, so they do.
You cannot prove aliens do exist, so they do not exist.
You cannot prove there is a ten foot tall pink elephant in this room, therefore there is one. Assume that 20 people have tested the claim by looking around the room, but only one claims to see the elephant. Is the absence of evidence ever evidence of absence?
Let's say we are all sitting around a picnic table and I make the following negative statement, "There is no picnic table here." Who has the burden of proof?
- Answers will vary, but it is important to understand that the first two arguments are both the fallacy of arguing from ignorance because both argue from a limitation of knowledge to a claim about reality.
The third argument about the pink elephant is not fallacious. This is because there should be evidence if there were a pink elephant in the room. The absence of seeing or feeling the elephant in the enclosed room is good evidence for inferring there is no elephant. In this case, the absence of evidence is evidence of absence.
In the final case, I have the burden of proof even though I am making a negative statement about the table not being there. This demonstrates the complexity of determining the burden of proof. Specifically, it is false that the person making a negative assertion always avoids the burden of proof.