There does not seem to be any evidence that corroborates this. The most I can find are claims that some records were destroyed, so we won't know. That doesn't automatically mean there is a connection, though.
It seems pretty uncontroversial that Kaczynski has participated in series of psychological experiments by Henry Murray. Do you accept this fact?
It seems to be well supported via anecdotal evidence that these experiments were quite brutal and stressful, one might even call them torture. Do you agree with this?
We know that the psychologist in question (Henry Murray) was associated with the Office of Strategic Services. Are you with me on this?
We know that the Office of Strategic Services is the predecessor of the CIA.
So what we know is that we have a researcher in the orbit of OSS/CIA who conducted brutal experiments on Kaczynski. So that is the connection you are looking for.
We do not know if these experiments were part of the CIA program running under the codename MKUltra, or if they were part of some other CIA supported program under some other codename.
> The most I can find are claims that some records were destroyed, so we won't know.
You are making it sound like mice got to archived papers or the ink faded. But that is not the case. The CIA director ordered all documentation regarding MKUltra to be destroyed in 1973. That is it. Those papers would have told us for certain what is the truth. They made sure they are destroyed.
As you say the fact that the documents were destroyed doesn't prove that Henry Murray's experiments were CIA backed. That would be crazy speak.
But it is also not entirely fair to say that there is no connection whatsoever. In the absence of hard evidence we won't ever know for certain, but we can make reasonable inferences.
If you disagree with anything I wrote in the above please be specific which part of it do you disagree with.
