I've really wondered about this before myself. I've decided for now, I love my therapist because he fills a certain need for me, to feel cared about, to be with someone safe, and he is also someone I like. My therapist though is not a blank slate. I don't think I know it all about him, but I know quite a bit. He might actually talk more than me in our sessions, I'm not great at talking. I think the problem with the "projecting myself" theory is that I don't love everyone. I don't even love everyone who is kind to me. It's impossible to pinpoint who I will love and who not, and the ones I love are rare, like maybe only 10 so far in my whole life. I work with a lot of nice people I know next to nothing about, they are perfect blank slates, and I don't think much about them one way or the other. Conversely I work with a boss I happen to know has the exact opposite politics and religion as me, and I find myself oddly very attracted to him, even though I know he is nothing like me, but he is a sexy man. I've had therapists before I didn't love, who were blank slates. I don't know... I just don't see as much rhyme or reason to it. Some of the things I love about my therapist are definitely things I'm not too, like I'm oddly attracted to his Jewishness, and I'm not even a little Jewish.