What do I do if I don't feel intellectually stimulated by my partner or in fact, anyone else?

Hello Phil, and thank you for your question. My first impression when I read your question is that it sounds like you are silently quitting the relationship. This may not be the case, but if it is, I would encourage you to reflect on why you were initially interested in your partner, and on positive memories and moments you've had together. If you find that there are not many, or that reflecting on them creates a sour taste in your mouth, it might mean that some level of resentment has seeded into the relationship.

Regarding your struggle to intellectually connect with others, it is possible you have not found  your "people" or that the way you are engaging is alienating. While you are right to say no one thinks like you do, your unique perspective does not have to lead to alienation. Rather, it can become a point of interest as you try to understand how others think, and express your perspective. It's minimizing to just assume those who do not think as you do are "inferior". Rather disagreement can lead to growth of the self and of others.

If you find yourself struggling to find a partner or friends, I would suggest looking at your values. What are the values you most associate with yourself? What are the values you want others to see in you? How can you go about finding those individuals with similar values. It is through aligning yourself with your values and finding those with similar values that you may find yourself in situations that are more intellectually stimulating.

Regarding your girlfriend specifically, I would reflect on the types of conversations you have and how often you feel yourself mentally rolling your eyes or actually engaging. As I previously mentioned you do not want resentment to set in on your relationship.

There are a lot of various factors to look at, and I suggest step one would be talking with your girlfriend and see how she feels in the relationship. You may find that she feels similar or alienated when you discuss certain topics. I would also suggest looking into therapy to possibly discuss in detail how you may struggle with connecting with others.