I'm 8 months into my PhD and have not done anything at all. I'm thinking of quitting, but the thing that stops me is I don't know what else to do now. But in order to make a rational choice, I want to know if I can continue my PhD even if I'm not passionate about the subject. I have always liked science and math and hence, chose engineering. I like learning about new stuff in general, but somehow I want to learn about everything else except my project related stuff.

This is a general should I quit post. There are some very good articles on the internet that answer this question better than we ever could. Though you can always continue on your PhD while you consider your options or apply for other jobs.

To answer your question from the other thread, impostor syndrome is generally where you feel like a fraud or got to where you are by luck. It is pretty common among PhD students who become overly anxious about their work/lack of progress and doubt their sanity. I am not a medical doctor and think you should investigate this yourself.