Yes it is by Bertrand Russell. It's in his introductory. Always read the introductory when it comes to philosophy. They almost always summarize bullet points of the idea their trying to get across. Here, he tells the difference between science and theology. Science tells what we can know, which is very little. And theology is based on things we can't possibly know. Whatever is inbetween is philosophy. I don't agree with Bertrand Russell's idea of philosophy, but that's partly because I'm not solely an analytical philosopher as he is. Don't fall into narrow categories. Strive in every direction, collecting ideas for your tool box.

Also, I can't believe you are going over Wittgenstein in an introductory course in philosophy. He is one of the greatest but most enigmatic philosopher the 20th century created. Scholars are still debating what he meant by his paragraphs. I don't have a primary text of his, but I do have a book called Wittgenstein's psychology, it was by Malcolm Budd I believe. The only thing I remember is The Beetle and the Box idea. And how the limits of our words are the limits of our world. Furthermore, how he believed there were no problems in philosophy, because he believed he solved it.

I once had a Wittgenstian professor who taught philosophy of mind. Great man. I couldn't grapple with Wittgenstein, even after frequent visits to his office. Wittgenstein is one of the greatest philosopher's of our time and he is what analytical philosophy gave birth to. He worked with Bertrand Russell and knew G.E. Moore.