Now, environmental science wasn't my major (we didn't have minors back then) but I still attended this guy's classes. And here's why.
To start off with, let me first explain why there was no need to attend his classes. He didn't care about the attendance - You would pass anyway. He didn't really care about marks in examinations - You would get a reasonably high grade anyway. But if you were interested in learning, he cared enough to make sure that you had every opportunity to learn.
I'm sure there are others more competent than me to relate anecdotes about him, but here's one anyway:
He once solved my entire quiz paper, right in the class when I told him that I couldn't do it - all the time, explaining each step of the solution. When I asked him why he did it, he explained that I was more likely to learn that way, than by getting a poor score on the quiz. I think I did.