Existence and the burden of proof
Isn't it interesting how our memories work? We sometimes remember these seemingly innocuous events or moments that would not have merited any consideration if we were to consciously compile the highlights of our life. Yet, they seem to be significant enough for them to remain in the forefront of our memory even as other memories and moments are lost in the murky mists of time.
One such incident that I remember occurred while I was studying at university. This was in the mid-90s. A bunch of my friends (of both the male and female persuasion) and I had gathered together at an apartment that was shared by a couple of the students. Those were much simpler times. Smartphones had not been invented yet. As such, our pastimes were a lot simpler and I would like to think a lot more wholesome as well. We played sports, hung out with friends, went to the cinema to watch movies, chatted (in person) and sang songs, as you shall see.
One of these wholesome activities that we sometimes partook in was a singing game (antakshari, an old Indian favourite). We would split up into two teams. One team would start by singing a song, or at least a fragment of it, mostly the chorus or the first two complete lines. The other team would then have to sing a song that began with the last consonant letter of the song fragment sung by the first team. (Note that this may not be entirely accurate as sometimes you could potentially base the next song on the last syllable, not letter, of the previous song). In any case, the intricacies of the game are not the subject of this post. Now, if any team was not able to come up with a valid song that fit the pattern, they would lose.
Being rather introverted, I tried to stay out of this for as long as I could and let the other members of the team contribute their suggestions and sing out the song when it was our turn. After a while, though, we reached a point where my team was stumped. We'd ended up with a letter for which none of my other team members could think of a song. I, on the other hand, did have a song that matched. I felt I had no choice but to sing it out to help my team, despite my natural reticence to do so in any setting where I could be observed by other people. I thought that my biggest challenge was to sing in front of all these people even though it was just a couple of lines of verse. Imagine my surprise and chagrin, therefore, when one of the boys in the other team (let's call him Mr. X), immediately after I had stopped singing, accused me of cheating. His contention was that the song I had sung did not exist. That I had made it up.
I was literally speechless. How could this be? It took me a few seconds to process this accusation. As I mentioned, due to my introversion I tended to shy away from conflicts. I did have to stand my ground, though. I knew I was not cheating; the song was real. Unfortunately, no one else in either group had ever heard it. How could I prove it? I thought it should not be that difficult. I had initially sung the chorus of the song. Maybe I could sing a verse, a few more bars to convince everyone that it was real. I proceeded to do just that, feeling even more self-conscious about it all.
Again, I was met with blank looks. My accuser, Mr. X, remained unmoved and unconvinced. Remember that there was no Google or Youtube. I had nowhere to go. Think back to those days. How could you look up a song? There was no easy way... I felt extremely stupid.
Something was rotten in the state of Denmark
I don't exactly remember what happened after that and it's not really pertinent to the rest of this discussion. What is important, however, is that there was something very interesting that had just happened here, something that rankled in my mind, something that threatened the natural order of things, a disturbance in the force. Something was rotten in the state of Denmark, or Brisbane in this case, but I could not put my finger on it. Over the next few days, it kept coming back to me and as I analysed it more clinically, I understood more clearly and logically what it was that had bugged me. The fact that this incident is still so clear in my memory is a testament to its impact on me, not least of which was the embarrassment of singing in front of a group of people, coupled with the accusation that I had cheated.
Analysing the cause of my unease
As I thought further about the reason for my unease, it seemed to me that there were two distinct things that were at play here:
the burden of proof: who was responsible for proving their position? As I had put forward that song, did it mean that I had to prove its existence? Or was the onus on the person questioning the existence of that song?
proof of existence or non-existence: could existence be proved? Could non-existence be proved?
These are both very interesting concepts in logic and which I intend to consider here.
The burden of proof (onus probandi)
Let us first consider the matter of the burden of proof. There are both legal and philosophical definitions of what the burden of proof entails.
In a legal sense, in most progressive countries, one is presumed innocent until proven guilty. The burden of proof, therefore, rests with the prosecution to prove beyond reasonable doubt that the accused is guilty of the crime, such as it may be. As the claim of guilt is brought in by the prosecution, so too are they obligated to prove that claim. The accused has no such obligation. They do not have to prove their innocence; the prosecution has to prove their guilt.
In a philosophical context, however, there is no presumption of any sort. If a person makes a claim which is then refuted by another (or even if it is not), the onus is on the person making the claim to prove it. This is actually a restatement of Hitchens's razor (note that, in philosophy, a razor is a formulation that eliminates lower-probability hypotheses in favor of those with a greater likelihood of being correct):
What can be asserted without evidence can also be dismissed without evidence
Hitchens's razor is itself a modern translation from the Latin:
Quod gratis asseritur, gratis negatur ("What is asserted gratuitously may be denied gratuitously")
Regardless of how you put it, the point of the assertion is that a statement that is not backed up by evidence can be summarily dismissed; there is no need to provide any contradictory evidence to do so.
Let's return to my example. I had sung a song. Mr. X had then posited that this was not a song and that I had made it up. Did I hold the burden of proof? While I had not made any specific claim, the act of me singing that song was an implicit claim that the song itself was valid. Based on that, it appears that the burden of proof was on me. One could also play burden-tennis (see this excellent review of Fodor's Psychosemantics by Daniel Dennett for more on this) but I will refrain from that. I will accept that I hold the burden of proof. I will, however, consider a counter position below as well.
That settles the issue of the burden of proof at least as far as this incident goes. Now, on to the nature of the claim and the subsequent dispute.
Proof of existence/non-existence
Given my acceptance that the burden of proof was on me, it then remains to debate how one could go about proving such a claim. Before I do that, however, we need to digress into logical philosophy again.
How can we prove the existence of something? Isn't this fairly straightforward? To prove the existence of something, all we need to do is produce evidence that it exists. I'll give you some examples:
If I claim that I have a $20 note in my wallet, I can prove that claim simply by opening up my wallet and producing a $20 bill from it.
If my son claims that there is a cookie in the cookie jar all he has to do is open the jar and produce it, something he does with annoying regularity.
If I claim that aliens exist, I would need to produce at least one specimen. That is all I would require in order to back up my claim - a solitary alien specimen. Needless to say, I (or anyone else for that matter) has not done that yet.
Note also that the evidence for existence must be provided. One cannot simply state that something exists simply because proof of its non-existence has not been demonstrated (the "argument from ignorance"). In the case of the last example, the inability to prove that aliens that do not exist does not prove their existence. It would be a fallacy to state that "You cannot prove that aliens do not exist so they must exist".
Clearly, proving the existence of things is fairly straightforward, at least conceptually. On the other hand, doing so may be difficult, such as in the case of that elusive alien.
Applying this to my example, all I would have required to prove my claim of the existence of that particular song was to produce a tape or some sort of recording of it. The case would have been closed. Unfortunately, as we saw, that was not easily doable in the 90s.
The counter-point of proving non-existence of something is even more difficult and nuanced.
How can we prove the non-existence of something? A claim of non-existence, or a negative claim, is a lot harder to prove than that of existence. Let's re-look at the examples from above:
If I claim that I do not have a $20 note in my wallet, I can prove that claim simply by opening up my wallet and going through all the bills in it. If a $20 note is not among the contents, then the claim has been substantiated.
If my son claims that there are no cookies in the cookie jar all he has to do is open the jar and look inside it. If it is empty, his claim is proved.
If I claim that aliens do not exist, I would be up against a much more difficult task. Unless a complete and exhaustive survey of the entire universe is done (an impossible exercise), we cannot definitively conclude that there are no aliens. Just because we have not found evidence of aliens yet does not rule out their existence. As the aphorism goes: "Absence of evidence is not evidence of absence".
The difference between the first two examples and the last one is significant; in the first two cases, the negative can be proven because we are dealing with a very limited scope of observation - the contents of a wallet or a cookie jar. In the third example, we are dealing with the entire universe. As such, proving non-existence of something whose scope could span the entire universe is an exercise in futility. One would need to be omniscient to achieve such a feat.
Absence of evidence is not evidence of absence
Let me return to the counter-claim of Mr. X; that the song did not exist. Let me tell you a bit about him first. He is a man of above-average intelligence and I respect him for it. In some ways, his refutal of my claim was a little perplexing. But then, no one is perfect. What did get me was that he, in his mind, tossed up these two options:
The song was real; he just had not heard of it. As such, he could simply take my word for it.
The song was not real. I had made it up. Now this is the bit that perplexes me. Did he really think I made up not just the lyrics of the song but also set them to a melody? Remember that I had sung a verse as well. Did he truly believe that I made that up too? Did he think I was part of the Lennon-McCartney duo?
Out of the two options above, he chose to go with the latter, on the one hand accusing me of cheating and on the other flattering me with some phenomenal lyric-writing and music composition abilities. An application of Occam's razor would probably have you rejecting the second option as it required way too many assumptions to be made.
In any case, Mr. X chose to go with option 2. As we have just discussed, this counter-claim is one that requires a proof of non-existence. For Mr. X to have proven his claim, he would have had to known every single song in existence, scanned through this list and satisfied himself that my song was not on it. While the scope of this problem is a lot more bounded than that of disproving alien life, it would still be very challenging to achieve. You could conclude that it was almost impossible to prove the non-existence of that song given the resources available to us in the 90s. Fortunately, Mr. X did not have to prove any such thing as the burden of proof lay with me. However, he still put himself in an awkward position by making a claim that could not be proven.
The point of this post was not to dwell on unknown, unrecognisable songs, my singing or song-writing ability or to reminisce about the good old days. Instead, I wanted to examine the concept of the burden of proof based on a real example. That led to the investigation of how claims of existence or non-existence can be proved. These concepts are germane to how we navigate through the information and misinformation that is peddled in today's media. We need to apply more rigour to information and claims of any kind before accepting it as true. If someone makes an outrageous or fantastic claim, we need to insist that they provide some evidence. I hope that that is what you, dear reader, do.
Till the next post, keep questioning.