Is there someone who can explain to me what the difference is between an irrational fear the Jews are taking over the world and say for example a paranoid delusion?
I suppose it would take a psychiatrist to answer my question but I can't help but wonder
Meh, I'm not going to claim to be a psychiatrist. But I majored in psych, and my wife works in the field. Mostly she agreed with this, but I get the impression she's 'dumbing things down' a little for my benefit.
In any case, a paranoid delusion is commonly coupled with auditory or visual 'evidence'. Someone suffering from a delusion will commonly have their fears confirmed or exacerbated by these, and will believe that an external source is providing them with information or insight others are unaware of. 'Voices in their head' may be safeguarding them information about something, for example. There are various organic and inorganic sources for these delusions, but in simple terms it's the sufferers own delusions providing the 'evidence' or fuel.
Irrational fear is less a clinical diagnosis, and more just a fear held despite a lack of evidence, or contrary evidence. These are commonly exacerbated by external sources, rather than internal ones. Demagogues make a career out of identifying and targeting these fears, and using them to unite disparate groups.
Common usage of 'paranoia', 'delusion' and 'irrational fear' might well mean the concepts all blend and blur in a colloquial sense. Also, there is nothing to say someone can't be suffering from an irrational fear brought on my their delusions. Just that not everyone experiencing irrational fears do so for reasons of delusion.
Eg. I used to be irrationally afraid of heights. No idea why. Over time I worked on this and was able to get past it. At no point was this related to a delusion.