@Alan McDougall,
Alan McDougall;47001 wrote:WLSleeth
Must reflect on this, at this stage I cant see how you can empirically prove a negativity
It is like trying to proving an impossibility
Well, you are mixing up two different things again, but calling them the same thing.
Why not stop referring to any testable situation as "proving negativity," that is what is causing the problem sorting this out. Let's examine how a proof goes.
First of all, the need for a proof begins with a statement about reality . . . no statement, no need for a proof.
Second, today we more or less accept empiricism as the standard for proof. We may use the term "proof" in law, where we allow circumstantial evidence to be labeled a proof; however, it is really a "common sense" assumption (discussed below), and no true empiricist would allow such a standard to be called a formal proof.
Third, there are two and only two recognized forms of proof allowed under the empirical standard: observation and tautologies. That is, if we can set up a situation to observe the actually of a statement, then that is considered a proof; any statement where the truth is contained with the statement is also a proof, such as the tautology, "all dogs are white, he is a dog, therefore he is white."
Obviously, a tautology is only proof its internal logic is correct, and not necessarily that the statement itself proves anything about reality. The advantage of the tautology only comes about when the premises are true, because then (if its logic is correct), the conclusion
must be true. Of course, mathematics makes full use of tautological proofs.
Fourth, since we are discussing an empirical proof, after a statement is made we determine if its assertion can be observed, and this seems to be where you are confused:
It is only whether or not an assertion can be observed that matters.
So if you say a weasel is in your pocket, and I have access to your looking into your pocket, then I can prove your statement true or false. However, if you say a weasel was in Caesar's pocket as he crossed the river, then I can not prove it true OR false; all I can say is, as was Hue-man's point, that it is improper to claim something is definitely true which we cannot confirm.
The concept of "negative proof" came up due to the very common practice in debates of claiming things like God doesn't exist because one can't prove it (arguments made in the last elections in the US were packed with this and other fallacies). There, one assumes something is untrue when it can't be observed, yet lots of things might be true which we can't observe (such as the Big Bang). The fallacy of the negative proof just means, assuming the negative of what you claim is true because the positive assertion can't be proven; that's how the term "negative" got hooked up with proof.
Two posts ago you also said:
Quote:Consider the extinction of the Yellow River dolphin. Pretty well all areas in which that animal can exist are under constant observation by a very large population that has the means to report its existence. So we can safely say that it no longer exists.
Now here you seem to be mixing up a two things again, the ideas of a formal proof and the "common sense" assumption (which some, like juries and judges, call a proof). For practical purposes we might assume there are no more Yellow River dolphins, but that is quite different from claiming it's empirically proven there are none. As long as we are unable to observe all places at once where Yellow River dolphins might exist, then one may yet exist; this has in fact happened, like when we discovered a living coelacanth:
YouTube - prehistoric fish
Of course we assume things for practical purposes all the time, if we didn't we get far less accomplished (a lot of criminals would not be in jail, for example).
To avoid confusion in discussions such as these, all we really need do is keep it clear in our heads what a formal empirical proof is, what the negative proof logic fallacy is, and when we are assuming something is true for common sense purposes.
