I’ve been following a discussion on Meetup.com where a guy is alleging that we are not true sceptics. I think his point is that we are far too pro-establishment and that a real sceptic has to be anti-establishment, almost by definition.I think this comment gets straight to a core difference between science-based sceptics (us lot) and conspiracy based sceptics. Conspiracy based sceptics seem to me to distrust claims from official sources, or at least the official sources that they have an ideological bent against. They take it as given that “the establishment” is lying to us, and therefore it is important to be sceptical of everything they say. Science-based sceptics are distrustful of any claim where there is no evidence to back it up. These are very different starting positions.The conspiracy position seems tempting. Official sources lying to us might seem quite reasonable at times. There are plenty of examples where that has indeed been the case. However it seems to me to be a very flawed position. They indicate that because someone is from a particular group, then they must be lying, irrespective of the content of what they are trying to say. Apart from this being a classic ad hominem attack, I can think of many situations where official sources have told the truth. I can also think of plenty of situations where anti-establishment folks have told bald-faced lies. So, being establishment or anti-establishment is no real indicator of whether you are speaking to reality, or telling pork pies. You have to assess the evidence as it exists.If conspiracy based sceptics will agree that official sources sometimes tell the truth, then what is their barometer for distinguishing between truth and lies? It doesn’t seem to me they have any real way to do this. The tendency is to look for an even bigger lie, so that their initial position can be preserved. This creates an enormous rat hole – and a vastly irrational rat hole at that – lies upon lies upon lies: a vast edifice built on nothing but suspicion and distrust.Conspiracy based scepticism is seductive, to be sure, but ultimately, it’s an irrational ideological position, and a dangerously misleading one at that.I want to contrast this with science based scepticism, which is about discovering the truth of a claim based on available evidence. Whether that evidence comes from official sources is neither here nor there. What matters is whether the evidence is good. Science based sceptics will accept official sources when the evidence is there, and reject it when it’s not. Sometimes, official bodies can be quite good with evidence: particularly when reputation and integrity are important, and concerns about public repercussions are high. Sometimes, determining the truth in a situation requires specialist skills and detailed scientific knowledge, something only professional bodies may have access to.One thing that science based scepticism has, that conspiracy based scepticism does not have, is a proper barometer. If evidence arises that supports a position previously dismissed, then the science based sceptic must assess it on its merits. If supporting evidence is shown to be wrong or fraudulent, then the sceptic must assess this too, potentially changing their minds based on it. Science based sceptics have to be willing to change their positions based on changes in the evidence base. They have to be able to admit that they might sometimes get things wrong.As a science based sceptic, I am ok with official bodies making claims, so long as those claims are based on good science and good evidence. I an also ok with non-official groups making claims, when those claims are based on good science and evidence. I am not ok with official bodies making claims when those claims are made up. I am also not ok with non-official groups doing likewise. Even if an official organisation is involved with something I might disagree with, I still must listen when they make properly supported claims. For me, it’s all about the claim and its supporting evidence, and less about the people making it – and that’s where science based sceptics are very different to conspiracy based sceptics.