I mostly believe political psychology is bullshit to the extent it predicts political positions based on "The Big Five" personality profiles but I find this man's background interesting.
At this time, you cannot study what people think or value. That's a nonsense. You can study what they say, including what they claim about themselves. But you can't escape that such things are motivated, and frequently we should assume are lies. Maybe one day we'll be able to read minds, intentions broadly, but we aren't there yet
You CAN study what people think or value. Because a lot of what they think or value is actually semi or sub-conscious, and is the result of their worldview. So you start with the implications of their ontological beliefs and suppositions, and move forward to why they think certain things are valuable, and why their patterns of thought cause them to reason that way. And sometimes they'll tell you, and sometimes they can't even imagine why they value or think what they value or think, because to them it looks like "common sense" or "obvious truth." But the key is in their ontological suppositions, their worldview, not something you have to interpret by reading minds. Just read their most basic beliefs.
