Another update on North Head: Am I in danger of changing my mind?

A few years ago, Martin Butler provided me with a copy of his book, “Tunnel Vision”, which I reviewed here. Last year Martin updated his book (The front cover calls it “An Explosive Update”) which I’ve now read and am in the process of reviewing. I think it’s a better book now than it was a few years ago, although I’m not entirely convinced by all of Butler’s claims. That is by-the-by, however, because earlier this week I met Martin at the Torpedo Yard cafe, at the base of North Head, and I came away from that meeting a little swayed in my thinking. I’m not saying I’m now a firm believer in the existence of a cover-up to hide decaying ammunition in one of the country’s most expensive suburbs. I am, however, willing to go so far as to say there are some anomalies in the public record which suggest there is more to the North Head story that certain authorities would have us believe.

I’ve been mulling this over the last few days. My good friend and colleague, Lee Basham (of South Texas College) has long argued that I should not have closed my book with a declaration that the best conspiracy theory about the events of 9/11 is the “Al-Qaeda was responsible” theory. Rather, Lee thinks I should have just provided the methodology for the analysis of conspiracy theories and left the generation of conclusions to those who would employ my analysis. His argument was that my analysis does not need to be hitched to any particular claim to be useful. The North Head issue is a good example: when Martin and I met in person for the first time one of the first things he said to me was “So, you’ve been a skeptic about all of this for a very long time, haven’t you?”

Being known as a skeptic of something has, in the past, been something I’ve celebrated and shouted to the rooftops. However, now I think that it can be a bit of a millstone. I have no issue in changing my mind; I went from being a very devout theist to an atheist (of the “There’s no good proof for the existence of the gods, so I’m not going to believe in them until there is” variety), and I went from being a racist to a non-racist. I even started out writing a PhD on the warrant of conspiracy theories believing that we had grounds to claim said theories were prima facie unwarranted, and we’ve all seen where that got me.

So, being known as a skeptic of the view there might be something more to the North Head story can be a bit of problem. This is because sometimes people take skepticism to mean “Here is my view on x, and you are stupid to believe otherwise.” However, my skepticism of the Hidden Tunnels conspiracy theory has always been about a lack of good evidence (and there’s a phrase which needs careful unpacking). Meeting with Martin and seeing and hearing about some of the new evidence he has brought to light, has shifted my thinking.1

Here’s a quote from the end of my book.

When inferring to an explanation, ordinary reasoners might fail to consider:

1. The extent to which the available evidence that the phenomenon being explained renders the hypothesis probable (the posterior probability),
2. The degree to which the hypothesis is independently likely (the prior probability),
3. The likelihood of the hypothesis, relative to the other hypotheses being considered (the relative probability) or
4. The possibility that there are some worthwhile hypotheses which have not been considered.

Three of these issues are to do with how we consider the probability of a given hypothesis. The fourth is about the failure of ordinary reasoners to consider other worthwhile hypotheses.
(Dentith, M. R. X. ‘The Philosophy of Conspiracy Theories’, Palgrave Macmillan, 2014, p. 147)

Martin’s research, at least for me, means there is new evidence to consider. His new evidence consists of additional information about the military use of North Head and how North Head fitted into the military command structure across Aotearoa. Not just that, but he also has some interesting examples of inconsistencies in official correspondence. Some of this evidence changes the posterior probability of some version of the non-official, conspiracy theory because it not just opens up holes in official reports and statements from Ministers and senior personnel, but it also shows that people where either very lackadaisical with the truth or that they lied to either the public or members of the Government.

Now, I say “some version of the non-official, conspiracy theory” quite deliberately; if I can going to concede that it seems there is more evidence for a cover-up than I initially thought, that doesn’t require me to believe a specific conspiracy theory that says, for example, that there is decaying ammunition deep within North Head. I can believe there is evidence for a cover-up about something without having to believe something about what is being covered up. But, and this is important, I think Martin’s research increases the likelihood that some version of a conspiracy theory about North Head is true. The question is, does it change it such that it is the most probable explanatory hypothesis?

Obviously there is a tension between the posterior and relative probability of a set of hypotheses; as the posterior probability of some version of, in this case, the conspiracy theory goes up you should expect it to become relatively more probable than some other hypotheses for the same event. This is where I am at right now: the new evidence certainly increases the posterior probability of some conspiracy theory about North Head, but has the relative probability of the rival, official and non-conspiracy theory been lowered, such that some version of the conspiracy theory is now the most likely explanation? For the moment, I have no concrete answer. My gut tells me that the official theory is still the most likely explanation, but it’s not as likely (to my mind) as it was a week ago. But why trust my gut on this, rather than go back and re-examine the evidence?

Which is what I am going to do. More on this soon.


  1. I keep wanting to say things like “a little bit” and I’m honestly not sure whether that’s because I’m simply resistant to changing my mind on some of the issues.

About Matthew Dentith

Author of "The Philosophy of Conspiracy Theories" (Palgrave Macmillan), Matthew Dentith wrote his PhD on epistemic issues surrounding belief in conspiracy theories. He is a frequent media commentator on the weird and the wonderful, both locally and internationally. On occasion he can be caught dreaming about wax lions but, mostly, it is rumoured he works for elements of the New World Order.