There should be a variety of methods to induce critical thinking. Discussions are the first, and most used, method for critical thinking, but it is surprisingly limited. Just like there are different ways people learn, there are different ways people best engage and provide feedback. You can write a well-developed response to a discussion post that uses minimal critical thinking if you know how to write well. You can also write a poorly-developed response to a post even though maximum critical thinking effort was made if you are not a good writer.