SA – “That is the first point you raise which indicates that you would rather explain the fact that this is extraordinary by just saying that it was perceived to be extraordinary and therefore it became a self-fulfilling prophecy. All of this with no evidence at all. That is beginning to look like a conspiracy theory.
[…]
– If you want to believe that this is a common health problem then that is conspiracy theory no.2”
SA, you seem to use “conspiracy theory” differently from the way I do; I wouldn’t count either mass hysteria, or a mistake, as conspiracy theories. For me, the theory would have to propose some group intentionally spreading mass hysteria or misinformation, for some nefarious purpose; a conspiracy theory has to include covert intent.
But that condition is necessary but not sufficient; it would amount only to a theory about a conspiracy, and conspiracies do occur.
To be genuinely a conspiracy theory in the derogatory sense (which is the only sense in which I use the term), the conspiracy must have almost supernatural power to control the evidence, and/or the accusations of conspiracy must expand without reasonable limit, eg. to 90% or more of everyone in an entire field of science. These 90% must be promoting wrong information not merely because, for instance, they are clinging to an established theory despite a new, better theory attempting to supplant it. They must be doing so despite knowing better, because the all-powerful conspiracy is coercing them by some means, ie. willingly or not, they are “in on it”.