I told the students in my class Mind, Brain, and Experience that we don't really know most things about neuroscience. That really the feeling of being a scientist isn't the feeling of knowing lots of stuff. It's the feeling of not knowing something that you're interested in. Kind of like not understanding a new relationship with someone who's important to you. It's the feeling of scratching your head and saying 'I wonder how this works', and saying to your grad student 'How do you think it works?', and doing an experiment that probably doesn't reveal the answer completely, but maybe reveals a little bit about the shape of the thing.
When I was in college, the professors I had all seemed to know so much. They seemed to be looking out from a high peak at the landscape below. But that's not the feeling at all. At least for neuroscientists, maybe all scientists. It's more the feeling of looking up at a huge waterfall, and not being able to see the top of it. You don't know where the water's coming from, and you're not sure how to get to the top so you can see where it's coming from. Is there a road that you can drive and get high enough to find out? There's no map. You don't even see a road, just a lot of vegetation all around. Someday someone might find a way to get to the top, but probably not in your lifetime. And instead of discovering the origin of the waterfall you'd like to discover something important about the brain and the mind, like how neural activity gives rise to thoughts, or even how the brain allows us to form habits that we can carry out almost without awareness.
You spend part of your work hours sharing what you know about the field with the undergraduates taking your class (and i love my CCNY students). Then you go back to thinking about pieces of experimental research findings that don't fit together well, and wonder how you might find out more about the waterfall.