evidence, existence, non-existenceI agree that absence of evidence is not evidence of absence, but I submit that there is NO better way of determining if something does not exist, for things in our day-to-day life.
Ask yourself if you have anything other than ‘absence of evidence’ to determine ‘no’ as the answer to each of the following:
“Do you have $1,000,000,000,000.00 Australian dollars in a Swiss bank account” “Do you have three legs?” “Is there an invisible object the size of an elephant blocking your door?” “Is there an elephant blocking your door?” “Is your cold gone?”
If you feel that logical contradiction or impossibility is superior, please remember the premise of how you determine non-existence on a day to day basis.
It is quite the pleasure to ask a theist who recites this mantra, and then turns round and claims exorcism gets rid of demons. How do you know that the demon is NOT there?
Add-on 1:
I feel that I need to expound on the question a little more, because it is being missed.
The focus is on ‘absence of evidence’. It is the only way by which I know that something does not exist. Now, that should not be taken to mean that if I show that I do not have a third leg, it conclusively shows that God does not exist.
No, no, no, no, no, no!
I also realize that just because we have no evidence, does not mean that there isn’t any. Said so right at the outset.
I also realize that other than “I exist” there is nothing else we can know.
Given all those things, is there generally any better way (not proof, I want nothing to do with proof) than absence of evidence that we use to conclude that something does not exist?
Answer to original question: Look for evidence. For example, I will use your questions. Each of them (other than possibly the last) can be refuted.
“Do you have $1,000,000,000,000.00 Australian dollars in a Swiss bank account” Check your bank statement.
“Do you have three legs?” Look down.
“Is there an invisible object the size of an elephant blocking your door?” Probe from underneath the door with a coat hanger.
“Is there an elephant blocking your door?” Use a small mirror of a rod to look under the door.
“Is your cold gone?” This one might be difficult to definitively test, though you could look at a blood sample under an electron microscope to see if there are any active rotoviri present. Assuming that you did this test while you had a cold, it would be pretty conclusive, though still not 100%.
Absence of evidence is an indication of absence, but you would still require more evidence.
Without evidence, it is impossible to know if something does not exist. Plain and simple.
You can however be reasonably sure. I’m reasonably sure that Santa Claus doesn’t exist. My parents told me that they were Santa long ago. However, as far as I know, Santa exists, he just doesn’t deliver presents to my house.
Think about Big Foot or the Loch Ness Monster. There is no proof that they don’t exist, thus people still believe that they do. Because of all of the hours spent searching with no real sightings, we are reasonably sure they don’t exist. But again, we have no proof.
So, in the end, the answer is find evidence supporting non-existence.
Response to your comments:
If you set the bar for evidence too high, it would be impossible to determine if anything exists. (Descartes) We have to assume that people can reasonably determine that something exists under reasonable circumstances. Seeing no leg and feeling no leg should be proof enough that you indeed have no leg. Besides, what is the difference between having a leg you cant see or feel, and not having a leg at all?
Final Edit
It appears in the end, if you need to prove that something doesn’t exist, you cannot.
Do we have cereal?
The answer to this question is the negation of the answer to, “Is the cereal box empty?” However, if looking into the box, and seeing no cereal isn’t good enough proof for you (invisible cereal), then you will not be able to ever prove to your standards that something doesn’t exist. On that same vein though, you cannot prove that you have cereal. Just because you see it, doesn’t mean it is there…In the end, this feels like a meaningless discussion.
There is never a need to prove that there is no cereal left. The empirical evidence is good enough. If we can’t see it or eat it, then it is as good as gone.
The problem is you’re talking a few very specific cases, where it is easy to claim privileged knowledge, and then you’re extrapolating that to the point where you’re making vast ontological claims about untestable objects.
It’s very easy to say, “I don’t have a third leg.” The definition of “leg” is very clear. If I had an invisible unknowable appendage that sprouted from my pelvis, it wouldn’t be a leg because it doesn’t have the properties that are associated with leg-type objects.
Likewise every other thing you said: every object is concrete and well defined, and it’s absence is trivially testable. For you to claim anything else leaves you mired in solipsism because you can’t know anything because nothing is testable.
In short, knowledge is a positive phenomenon. I believe I have two legs, because a leg is a specific thing, and I can test that I have them. I may have a zillion unknowable extra legs, but I’ll never know, because they can’t be tested. Moreover, all my knowledge is based on sense data, which could be flawed or mistaken, so I have to hedge my bets and say that, to the best of my knowledge, given the data that I have access to, I believe this or that thing exists.
I am also entitled to believe that things do not exist, for the same reasons. But it’s only a belief because I can’t test an absence. I don’t think god exists. I’ve never seen any evidence that suggests to me that god exists. But if there were an omniscient, omnipotent being hanging around, and they didn’t want to be known, what the hell could I do about it? I couldn’t trust my sense data, and without that I’m back to cogito ergo sum. So I believe that god doesn’t exist, but I don’t know.
Define what the things are for which you want the answer to the question "Does this thing exist?".
In some of these definitions, there will be active predictions about the sorts of events we can expect to see in the world as a result of these things and the lack of these things. For example: suppose there is a room filled with one unknown gas, this is the only information about the room that you have. But if I tell you that if I place a algae that will survive if and only if nitrogen is present, if that algae dies, you can say with high certainty that there is not nitrogen in that room.
To use one of your examples - in the case of a third leg, I should expect:
to see a third leg near my other legs
to use a third leg while walking
to need to wear pants with three legs...etc.
This is of course assuming that the definition of the leg includes things like, my legs are near all of my legs, my legs are visible, they are used to walk, i need to wear pants that fit around my legs, and what not. If you start changing this definition (e.g. that the leg will not be near all of my legs or even near my body) then it becomes more difficult to refute this assertion.
The take home point: it is only to the degree that your definitions are constrained that you can learn about something's non-existence.
Nonetheless, so long as you can find cases where some property/event does not occur, in cases where the definition would include predicting that property/event would occur, absence of evidence (of that property/event) can be construed as evidence of absence.
*Note:*This is how science progresses, theories make active predictions about the presence or absence of a phenomenon, and if that phenomenon does not occur, we need to adjust the theory. This is not philosophically invalid, but it does require very clear definitions to work.
To respond to your original question though, you don't necessarily need to know that something does not exist. It can merely be your working hypothesis that fits best with your data, given your prior probabilities over the data. To see all that I mean check out this article on Bayesian epistemology.
You can prove X does not exist by falsifying it — by demonstrating when X is false. Sometimes that means where X just stops, and sometimes it means where Y exists in place of X. But you also need to prove when X is true.
What methods do we use to prove X is false or true? With our senses, and with machines which can measure and detect (and report back to our senses).
With mundane, day-to-day things, these methods are sufficient to falsify X. That’s because day-to-day things are finite. They are measure-able, so we can measure where they start (where X is, so X is true) and stop (where X isn’t, so X is false). You can hear where the dog is or isn’t, see if there is a box of cereal in the pantry or not, feel if you indeed have a third leg.
Once you go beyond day-to-day things, it is harder to falsify X, because X is now in the realm of the infinite. The universe is infinitely big. We cannot measure it completely. So we can’t determine the size of it, genuinely (that is, if X is “the universe” and at some point the universe ends and something else Y starts, that “some point” is the spot where X, the universe, is now false).
“Is there a deity?” falls into the category of “Things Which Are Hard to Falsify,” because somewhere in this infinitely large universe might be a deity. We can’t measure everything. We can’t find where X is true, so we can’t find the point where X stops being false.
What we can do is say “So far, everywhere we’ve measured, in every way we’ve measured, using every method, by everyone who has ever measured, where X = ‘is there a deity?’ X has turned out to be false. We’ll keep looking, but our working hypothesis is that X is false everywhere — that there is no value ‘true’ for X.”
What this means in day-to-day living is that we behave as though we have already falsified X.
It seems most of these are Popperian defenses. This question is compounded with at least three easily identifiably rational components that must first be addressed.
Let’s go on and define a few terms too:
Now, I’m going to answer this with a rational rebuttal from a materialist’s perspective.
If your ontology is of a materialistic sort then you don’t believe in non-material proofs (whatever that might be). This is not something anyone can prove; they simply are not permitted within a materialist’s world view. This is undeniably and inherently vicious and circular: you’re essentially claiming you don’t believe non-material things can be known through a non-material method of knowing, because you would deny such method of knowing. This breaks down the topic into a few statements, which the burden will be on you to defend:
None of these should require much explanation. If you can convince someone that materialism is a better world view then God is excluded. Now we address the whooper:
What would make the statement, “I know something does not exist” true.
I’d argue that knowing something does not exist must be differentiated from, “I believe something does not exist”. And, in that you’ll find the light at the end of the tunnel. Either,
is invalid. Or, it is either the same as, or different from (tautological truth):
For me, I want affirmative claims of non-existence to be useful and valid so I just tack on the addendum “as far as I can presently know from the material evidence I have”. I’ll make the bold claim that this addendum is also implicit when this claim is made by any sane person – including whomever I’m speaking to. Here is a useful quote stolen from the wikipedia article about evidence and the absence thereof
“In some circumstances it can be safely assumed that if a certain event had occurred, evidence of it could be discovered by qualified investigators. In such circumstances it is perfectly reasonable to take the absence of proof of its occurrence as positive proof of its non-occurrence.” - Introduction to Logic, Copi, 1953, Page 95
Wikipedia further goes on to use I know there is no change in my pocket, as a practical example of this non-violation of the “evidence of absence” fallacy. I could expand on this:
I would maintain the former has been exhausted… We can affirmatively state the later. As far a materialist can know or not know, we know conscious aliens do not exist in our solar system. The stance that the subject is not there is the only sane and rational one if you’re a materialist with no further evidence, no evidence to the contrary, and no further experiments you could perform within reason.
These are the same assumptions you would make to some claims in the affirmative:
“Know” might be picking up a new meaning when you’re affirming the negative, but it should be polysemously expanded to encompass that for materialists. Does this make it fair to state that a materialists truly “knows that something does not exist”? Yes, I think if you understand the worldview, and the axioms you’re building on; and, you disregard that there is no telling defeat of utter skepticism.
This very question comes up in different tones, language (logical, english, gibberish, et cetera) in different areas of studies. But let’s tie it together and see where we are.
Let’s talk about something else first:
Given a collection of infinite but countable boxes, to prove that something exist, compared to proving something does not exist, would require less time. (and thus is easier)
The reasoning is quite simple if you disregard the use of mathematical symbols. Think about it, if it exist in kth box, then the time needed to prove that it exist is k times the time needed to check each box, which is a finite amount of time. The converse, if it doesn’t exist, then the time needed to prove would be to search all boxes, which means that the time taken would be infinite.
Look into our universe. You can say it’s expanding, you can say it’s collapsing, you can say that it’s something in between, anything. But there is, in effect, practically infinite area for you to search before you can conclude.
And well, we have something called black holes, and very delicate thing called event horizon surrounding it. There, the very nice time-space relationship would mean that proving whether something has been thrown in is impossible.
Lastly, the characteristic of an object that you wish to prove its existance may not allow detection by your specific way of seeing it.
Human beings, day to day, are not tasked with determining whether something does or does not exist. We act upon the things we can, we worry about the things that have caused us anxiety in the past, we are pragmatic animals.
We have leisure faculties, and they can be used to imagine qualities like existence, and we can extrapolate the imaginary quality of non-existence from it. We can engender existential crises in our minds when cognitive dissonance carries us away; but those are just rational incongruities fighting it out, not some psycho-spiritual awakening . Yet the fact remains, the tautology of existence and non-existence is nonsense.
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