Let's put this common refrain to rest~ something that I hear all the time in arguments concerning religion.  It goes something like this:

" Remember, you can't prove a negative!"

Really people?

This has become much more common, especially in the arguments amongst Atheists and agnostics concerning certainty, and it really puzzles me how people can be skeptical and free-thinkers, yet take to an idea so easily and not question it.  I will elaborate on this a little more once I have the time, but let me start all of those "can't prove a negative" types off with a question~ " I am not sitting at my desk."  Thats a negative claim.  Are you telling me that there is no way to confirm or disprove that?

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@ John:  Fail.  Please see Rich's comment above.

If you state that there are no elephants anywhere, and you didn't have any evidence of elephants at all, you could say you cannot prove a negative. Do you see what I mean?


If you ask me what I know about whether there is a God, I would have to say I can be 99.9999% sure. If you ask me if I believe there is a God, I would say I 100% believe there is no God. 

If you are honest with yourself, and you ask yourself whether you know, according to science you can never really know with 100% certainty because you require evidence and you cannot prove a negative.

But if you ask yourself whether you believe there is a God or not, you can reach 100% because believing requires no evidence.

About that... I wonder if you should instead be asking about the personal identity and behaviors that sustain the concept of a god-- because it's not the concept itself that matters, it's only the places where it interfaces with themselves that people actually consider. The rest is often just mental goo to support the behaviors they'd like to protect.

Well, Cane, that's exactly the point of my argument: the incompleteness limitation (from above) makes it impossible to determine if a search has been exhaustive, so you can't use an exhaustive search to prove a negative. 


You can, however, take a different approach and prove that a possibility is incompatible with the current set of attributes-- which means that combination cannot occur at all, completely regardless of how much searching you've done. That's how you bypass the incompleteness limitation and prove a negative statement.


The only real constraint in this approach is that you must have a plurality of attributes to consider, so you can't ask a single-property question like "Can there be red?" The question has to express at least one control attribute to compare against, so a viable question would be "Can the human eye perceive red?" The former question cannot be answered, but this one can demonstrated as true (by a search) or false (by incompatibility). 


Or to take John D's example, "My office is smaller than an elephant; I can therefore conclusively exclude the possibility of an elephant being in my office." No search is necessary if you can show that an incompatibility between attributes makes the possibility self-contradictory (since the statement implied a full-size, adult elephant).


The main way to bypass exclusions is to find "near-matches" that avoid the conflicting attribute by suggesting alternates like a pygmy elephant, baby elephant, time-travelling elephant with an invisibility cloak, etc-- but the exclusionary statement still stands and you will not find a full-size, adult elephant in the current office.

Hello Drake,

To whittle all that down you come to this statement: Knowledge requires evidence, believing requires no evidence. 

You can believe that something cannot exist, and I am not saying it is not a valid belief, but you can never prove it with the scientific method. You can convince someone to believe in "proof" of a negative, but all you are really saying is due to the rules of logic, it cannot exist. There is no evidence either way to substantiate the proof of a negative. See what I mean. It is language vs. evidence.

The first bit was way in the wrong direction, but the second part was just about right. Here's the miniature version of my argument:


Logical deduction can be applied to positive proof to exclude new possibilities by pre-emption. Essentially, if you have an "A or B" situation and you know A is true, then you have also proven "not B".


Besides that, I am somewhat leery of how you're using 'belief' and 'evidence' because it comes across as somewhat dogmatic. Is it the scientific method which determines the truth or falsity of data, or is it the rules of logic which judge the data collected by the scientific method? If is the former, then logical deduction probably can't qualify as proof (or knowledge) in your philosphy.

If A or B, A is true, then not B requires that you prove A. How do you prove A?

If you use your prior "knowledge"(what I call belief), you can convince yourself of the truth of A, or in other words, you can believe that A is true.

If you get evidence of A, that can strengthen your belief that A is true, but then what is knowledge? I guess I do not know what most people define knowledge as. Is it memories of something being true? I don't know.

I do know that without evidence, we cannot really determine if something is true or not. To get the identity of A, I need evidence of A, even if that evidence is only light bouncing off of A and reaching my eyes causing me to form a belief that A exists.

If you have evidence that God is real, then the method you used to gain this evidence must be repeatable by others, or your evidence is not really evidence. What is evidence? Evidence is that which acts on our senses.

What is truth? The belief that something is as it is thought to be. For example: An apple is red. You judge that to be true by searching your memories of evidence for something that is a red apple which is used to strengthen your belief that it is true.

Can you believe something is true, or can you know something is true?According to your rules of logic, both cannot be true. Or can they be? If belief = knowledge, then they could be both true.

The rules used by logic are tools we use to augment our perceptions just like the scientific method is. Both tools are valid.

This will be a lengthier response than I would prefer to give, but here's how I would lay out the fundamental parts of knowledge:


Interaction, observations, etc. become data, which can be stored either internally (memories) or externally (recorded). 


For the purposes of decision-making, humans regularly generate evaluations of this data to drive optimally-beneficial choices.


"Belief" is merely the recognition that you have previously made evaluations on a topic (with the data available at that time) and is only relevant as a 'sunk investment' of effort.


Given indications that an evaluation must be re-done, there are two options to follow: rebuild the evaluation at additional cost (the physical solution), or establish attention blocks to hide the issue with only minor investment (the mental solution).


The goals of science, philosophy, and any intellectually-rigorous approach to the world is to consistently follow the physical solution, despite the additional short-term costs. "Dogma" is the willingness to follow the mental solution because it 'protects' the integrity of their past evaluations with only a lazy effort.


So the real enemy is dogma, while 'belief' is a neutral and generally inconsequential part of decision-making. Knowledge is strictly data, not belief, and 'truth' (I would rather call it veracity) can be measured by how closely one's mental picture matches against the physical picture. 


The scientific method, at its core, is merely a set of techniques for filtering out non-contextual data (which are invariant across time and space) from the higher-level contextualized data (such as social interactions, etc). Since interactions only filter up, not down, contextualized data can be pre-emptively eliminated from evaluations of non-contextual, invariant phenomena.



Jason, that is exactly the foundation I have been working from. Exclusion by logical contradiction is commonly applied a priori (to borrow from Kant), while my argument is to extend that capability to a posteriori exclusion based on any set of acquired data.


"Compatibility" is really based on identifying EITHER/OR relationships and using positive proof of one TRUE to preclude the possibility of a second TRUE. This preclusion is functionally identical to a FALSE, so it simulates positive proof of a negative statement.

Cane, you say, "I do know that without evidence, we cannot really determine if something is true or not." We may not be able to prove something is true without evidence (though I'm not sure about that in the case of things like math), but it is easy to prove that something is not true without evidence if you can show that it is logically impossible. This has been done repeatedly on this and the "100% Certain" thread (providing ample evidence), and yet you really seem to want to ignore the idea.


If you insist that nothing can be known without evidence, then yes, you cannot prove a negative. Unfortunately, "you cannot prove a negative" is a self-negating proposition, since it is, after all, a negative itself, so how do you know it's true? (Hint: It isn't.)


You can, and apparently are, simply assuming it as an unquestionable axiom, but we have shown you over and over that this axiom is very questionable, and in fact appears to be demonstrably false. When your axioms are punctured, you need to take a step back and look at a larger picture. You don't seem to want to. That sounds like dogma to me.

I do not agree that you can prove anything without evidence. Logically, all you can do is form a belief that something without identity cannot exist. That does not mean that in fact it does not exist.


You can have evidence of an identity and come to a belief that it exists, but to know it exists, you need evidence.


I can give you the identity of an apple, but if you never had any kind of evidence to your 5 senses of an apple, all you can do is believe that an apple exists, but you cannot know it until you see, taste, feel, hear, and/or smell an apple.


Just because you do not have an identity of something, does not mean it does not exist. If you have a conflicting identity, the identity is wrong. That's all.


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