I am sure most of us are familiar with this, but for any who are not:
"I found that those of my friends who were admirers of Marx, Freud and Adler, were impressed by a number of points common to these theories, and especially by their apparent explanatory power. These theories appeared to be able to explain practically everything that happened within the fields to which they referred. The study of any of them seemed to have the effect of an intellectual conversion or revelation, opening your eyes to a new truth hidden from those not yet initiated. Once your eyes were thus opened you saw confirming instances everywhere; the world was full of verification of the theory. Whatever happened always confirmed it. Thus its truth appeared manifest; and unbelievers were simply people who did not want to see the manifest truth; who refused to see it, either because it was against their class interest, or because of their repressions which were still "un-analysed" and crying out for treatment.
The most characteristic element in this situation seemed to me the incessant stream of confirmations, of observations which "verified" the theories in question; and this point was constantly emphasised by their adherents........... The Freudian analysts emphasised that their theories were constantly verified by their "clinical observations". As for Adler I was much impressed by a personal experience. Once in 1919, I reported to him a case which to me did not seem particularly Adlerian, but which he found no difficulty in analysing in terms of his theory of inferiority feelings, although he did not even see the child. Slightly shocked I asked him how he could be so sure. "Because of my thousand fold experience, he replied; whereupon I could not help saying ;"and with this new case, I suppose, your experience has become thousand-and-one-fold."
Plus ca change... and all that.
The quotation is from Karl Popper, Conjectures and Refutations.
Somehow it seems to make it worse that these ideas were disseminated in London University sixty or so years ago.