Is an argument from ignorance ever valid?


Is an argument from ignorance ever valid?

What about sense perceptions, can I truthfully say that I do not see the elephant in the living room, if I do not know that I am seeing it?

What about death? Supposing (and excuse the idea) I won't ever know that I will "die", can I die?


Posted 2017-06-23T00:01:24.110


Question was closed 2017-10-04T00:19:43.633

what about innate ideas? if knowledge of X is innate, and i do not know that X is Y? – None – 2017-06-23T00:10:22.480


Sense perceptions are not arguments, nor are reports (correct or not) based on them. And to argue from ignorance would be to conclude that you will not die from not knowing if you will. Could you please explain how your examples relate to the argument from ignorance.

– Conifold – 2017-06-23T00:28:57.157

not sure what you mean, that we can't argue that we don't see something? seems quite possible @Conifold unless you just mean that no such thing should ever figure in philosophy? as to the death comment, that is what i said, yes – None – 2017-06-23T02:56:04.487

One can argue over seeing something or not, but what one can say truthfully is based on what one believes. One can doubt reliability of one's senses, or one can also come to change one's perceptual belief as a result of some argument, valid or not, from ignorance or not, but forming a perceptual belief from sense perception is not an argument. In any case, one can get true conclusions from invalid arguments, so it is unclear why your examples show that ad ignorantiam would be "valid" even if what is asserted were true. – Conifold – 2017-06-27T01:14:55.153

Yes - ignorance is bliss! That's meant to be a joke. – Mozibur Ullah – 2017-08-04T16:19:44.433



In discussions of appeal to ignorance, one common distinction is between "absence of evidence" and "evidence of absence." "Absence of evidence" means that no or very little evidence is available either way (neither for nor against the proposition in question). Is there life on Europa? We don't yet have evidence either way, so concluding that there is life on Europe would be fallacious. There's a lack or absence of evidence. "Evidence of absence" means that there is evidence that something isn't there. We've looked for life on the Moon, and gathered enough negative evidence to be reasonably confident that there is indeed no life there. There's sufficient evidence to conclude that life is absent on the Moon.

There are at least two complications worth mentioning here. I'll illustrate this with a chemical safety testing example. Suppose we want to know whether chemical X causes cancer. We've run one small study, in lab rats, and the effect was not statistically significant.

First, the basic difference between "absence of evidence" and "evidence of absence" is whether we have "sufficient" evidence, or can draw "reasonable" conclusions. But different people may want to use different standards for sufficient evidence. The manufacturer of chemical X might claim — based on the one small study in lab rats — that we have sufficient evidence to conclude that chemical X does not cause cancer. They see this as a case of "evidence of absence." But environmentalists might claim that this study doesn't provide sufficient evidence to draw any conclusion. They see this as a case of "absence of evidence."

Second, when we're talking about practical reason, we may have good reason to act as though a claim were true even if we don't have good reason to believe it. For example, environmentalists might maintain that we should limit the use of chemical X — treating it as though it did cause cancer — even though we don't have good reason to believe that it really does cause cancer. This doesn't mean that we should simply assume that chemical X causes cancer on the basis of no evidence. Instead, the idea is that the default position is that chemical X causes cancer, and we need sufficient evidence to conclude that it's safe. (The manufacturer, on the other hand, might argue that the default position should be that chemical X is safe, and we need sufficient evidence to conclude that it's dangerous.)

Dan Hicks

Posted 2017-06-23T00:01:24.110

Reputation: 2 337


If by argument from ignorance you mean the wikipedia definition that "It asserts that a proposition is true because it has not yet been proven false (or vice versa)" then the answer depends if your talking meta-physically, i.e. reality, or practically, i.e. whether or not you would be justified in believing a proposition.

For meta-physically, it is never valid. Things are true or false regardless of whether someone has proven it to be true or false. For example, water has always been composed of 2 hydrogen molecules and 1 oxygen; it doesn't whether or not it's been proven true or it's negation false.

Practically, it can be valid. A classic example is "innocent until proven guilty."

For your second question, I'm assuming that when you say you "do not know that I am seeing it" you mean that you don't know the definition of elephant. In that case, it's not really a matter of truth but a matter of two people not understanding eachother. If you mean that you don't know whether or not you are seeing whatever the thing is, that's impossible. People are always aware of what they are seeing because they are seeing it; whether the thing exists in reality is a different question.

For your third, yes you can die even if you don't know it. Just because you didn't predict something doesn't mean it won't happen. For example, if someone sneaks up on you and stabs you, then you got stabbed; it didn't matter that you didn't know it was going to happen, or even that you don't know what stabbing is.


Posted 2017-06-23T00:01:24.110

Reputation: 111

I disagree with you're statement "If you mean that you don't know whether or not you are seeing whatever the thing is, that's impossible." If you're under the influence of a psychotropic drug, you cannot assert what you see is what it really is. Beyond drugs there's always Descartes' Deceptive demon principle which boils down to, the only thing you can be certain of is your own existence; I think therefore I am. Otherwise, I think the Innocent till proven guilty is the best example of argument from ignorance. – Void Serpent – 2017-10-03T17:57:25.567