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Question: Can someone kindly help me with the adage, "You can't prove a negative"!.!.!.!?
First off, I have no formal training in philosophy, so I apologize in advance if I don't have a strong grasp of the terms involved!. Often, in the context of, say, a new drug, scientists will say we CANNOT prove that drug X WON'T make anyone grow a tail (just for the sake of argument)!.

The central issue is that in this example in order to prove this negative assertion, we'd have to try giving the drug to every human being alive before we can make this assertion with absolute certainty!. If I were to assert drug X CAN help reduce blood pressure, however, I can do a simple experiment which can prove my assertion!.

A lot of this has to do with the differences and inherent limitations of of deductive versus inductive reasoning!. I suppose it may come down to a matter of degree of confidence that a negative assertion is true, e!.g!. there is no tooth fairy!.

Can someone help me understand why there seems to be this dichotomy between why those in science hold fast to this mantra, i!.e!. that one cannot prove a negative, whereas in philosophy, there is a greater comfort in proving negatives, (e!.g!. it's not diffiult to prove that ten does NOT equal twenty)!?

Why are scientists less inclined to acquiesce that negatives can, indeed, be proven true as opposed to philosophers who are more comfortable with this matter!?

(For additional info, please google "you can't prove a negative," since the system is not allowing me to add links to my Q's at this time, in case you're unfamiliar with this adage)!.

Thank you graciously for your help!.

Best Answer - Chosen by Asker:
The problem is a bit more complicated than that!. Let's use a different example to highlight the problem!.

Here's a negative: Leprechauns don't exist!.
Can we prove that leprechauns don't exist!? Not really!. We can't just look everywhere: according to legend, they can turn invisible!.

All evidence is left by things that are in existence!. Thus, the very nature of evidence can only be used to prove existence!. If something doesn't exist, it leaves no evidence to prove that it wasn't there!.

Now, you might say that, "if leprechauns existed, then we should be able to find X," where X is some sort of evidence that only a leprechaun would leave!. But what would that sort of thing be, and how would you know to look for it!?

In short, you can't prove that leprechauns don't exist!. You either believe it on faith, or you do not have that belief!. You are correct in that it comes down to degree of confidence that a negative assertion is true!.

The confidence you are noting isn't between disciplines: it's a difference between the types of things considered!. To use your example, ten and twenty aren't equal because we don't define the quantities in such a way that they're equal!. It's a very different thing when you're trying to determine the allegations of existence or the nature and attributes of existent things (which plays into whether or not a drug could be expected to cause tail growth in humans)!.Www@QuestionHome@Com

People prove negatives all the time, that a fundamental part of science since if you prove any thesis you automatically disprove it's antithesis!. Police prove negatives all the time, it called an "alibi", if you were in California at the time of a crime you weren't in Georgia committing it!. Attorneys also prove negatives, it's called "exculpatory evidence", if the guilty person had type A+ blood and the suspect is type O then he wasn't the guilty person!. To say you can't prove a negative is essentially saying you can't prove under any circumstances by any means whatsoever that a man isn't a woman!. I don't know from where that idea came or why it persists, but people won't let go of it!.Www@QuestionHome@Com

I'm not big on philosophical terms, but I've always looked at the whole "trying to prove a negative" thing as a matter of an inability to collect data on something that doesn't exist!. There was a funny Doonesbury comic right before Obama was elected concerning this!. The main character, Mike I believe, has a daughter who's a teenager helping the Obama campaign!. When McCain was saying horrible things about Obama like he's a terrorist and whatnot the campaign members gave her the assignment of "proving that Obama isn't (various things)" so she says to the older staffers "Isn't this proving a negative!? Making it impossible to prove!?" The older staffer says, "well yeah, that's why we give it to the newbies!."

Aha I thought it was really funny, but in scientific reasoning one must collect data on something in order to prove it exists!. If someone says 'prove to me that my thousand-armed, octopus-like god doesn't exist' for example, there's really nothing I can do, you can't provide data about something that doesn't exist!. What would the data be!?Www@QuestionHome@Com