How likely do you think it is that someone can be right about some things but entirely, shockingly wrong about other things?

That sounds like me. Brilliant one minute, an idiot the next. That's my general experience. Glad to be the first one to answer at your homecoming.

I think that could describe us all, at some level. 

How likely? 100% likely.

But no matter how far the sciences develop, it's not possible for any professional to be always right. 
Psychoanalysis, medicine and paediatrics are by their nature, imprecise fields.

Psychology is an infant discipline compared to other sciences. Freud published his first theoretical work, Studies on Hysteria, in 1895. In it, he proposes the idea of the unconscious - which no one had dreamed of before that time.

In the early days of psychoanalysis, cultural bias (patriarchal assumptions about women) played a significant role in creating false theories.
The Oedipal theory was a deliberate fraud to hide the prevalence of incestuous rape in society - to protect men's interests.
Consider the term hysteria: "1. exaggerated or uncontrollable emotion or excitement; 2. an old-fashioned term for a psychological disorder characterized by conversion of psychological stress into physical symptoms (somatization) or a change in self-awareness (such as a fugue state or selective amnesia)."
The term derives from the Latin for womb. Freud coined it to reflect his view of the cause of his female patient's neuroses.
It's a field many others have already explored and written on - exactly how and why Freud got it so wrong.

One thing is certain. Every theorist will be prone to the same kinds of mistakes based on cultural biases.
The problem is that few humans can see outside their own cultural frame of reference - unless they've travelled a lot and studied how others think.

Compare the start of psychology with the that of physics.
Democritus's first notion of the atom in 600BC Athens - or Isaac Newton's theory of gravity in 1686.
Physics has had far more time to speculate, test and double-check.

Consider mechanics. A car breaks down. It has certain symptoms which could suggest several causes.
The mechanic always looks for the cause by a process of elimination.
What is the most common or statistically likely cause?
Which are the easiest parts of the engine to access?
What are the easiest and cheapest tests?
Most times, this will help him solve the problem quickly and efficiently.
But it also means that some of the time, the cause of the problem won't be so easy to find.
He has to keep going until he finds it - with the time and expenses climbing.

Much medicine is mechanical - the way blood is pumped, the air is filtered, and so on.
The way biochemical and bioelectrical systems work requires a similar kind of logic.

Psychoanalysis is even more imprecise. It's closer to the humanities than the sciences. A good psychoanalyst does very little beyond being a good listener and asking good questions. He or she merely facilitates. It's the patient who does the real work of learning to understand him or herself.

One of the inherent risks in medicine is that doctors must inspire confidence.
Double-blind tests have proven again and again that across all fields, the placebo effect accounts for about 30% of all healing.
10% is regarded as clinically significant. 
So to get the best advantage in healing, a doctor must convince a patient that the therapy will work.
If that's not possible, they may take the next best approach - that, given the statistics, their particular situation means this treatment will give them their best chance.

Our problem is that we often try to place too much hope in a system that is imprecise and cannot deliver perfect results.
The miracle is that the system manages to provide satisfactory results more often than not.



This post was edited by inky at August 19, 2019 1:34 PM MDT

Bookworm stole my answer. 

~

It not only possible but probable. The other theory is that you are right about what you agree with and shockingly wrong about what you disagree with.