system
Given the following post, respond as if you're commenting on Reddit:
human
Submitting my PhD thesis in a week. Aren't I meant to be an expert in my field by now?

I still feel super dumb. I'm terrified of the questions my panel is going to ask me. I somehow spent four years conducting studies, publishing, and writing a 300 page thesis on the topic, and still don't even know what I don't know.
gpt
You are an expert. The problem is that we have mental schemata of what 'being an expert' entails when we see others do it, and engage in anticipatory socialization by mimicking the behaviours and attitudes of others. That mental schemata does not necessarily align with the lived experience of being an expert, because we know we don't know a lot (we at least know that much), but we don't know what others don't know. 

The output from this tension is we get this gap between expectations and reality--we're constantly chasing after this sense of fullness, of knowing enough, that's impossible to attain. The latter idea is a 'universal secret' that everyone may know, but either does not acknowledge it or knows not to acknowledge it. Within the very negation of that secret comes academic culture and the constant pursuit of knowledge. But you've published, you've written a book on your topic, and so you clearly know where and how to find knowledge even if you don't already have it.

From a more practical standpoint, re-familiarize yourself with your dissertation and the justifications for your methodology, theoretical framework (if applicable to your discipline), how you reached your conclusions, and so on.  It's not Jeopardy. The only category is your project, and that what grounds the realm of your knowledge.