Generally speaking, a person’s total worldview consists of how he sees the world in three broad categories: Spiritual, Moral, and Scientific. These three areas represent life’s big questions such as: What happens after we die? (Spiritual); Are right and wrong absolute? (Moral); How did life come about? (Scientific), etc. So Spiritual, Moral, and Scientific skepticism are three of the four kinds of skepticism you can expect when you engage a skeptic.
The fourth kind is Biblical. The Bible is the lens through which believers view the other three categories. Although skeptics don’t use the Bible to shape their worldview or to guide their life, most will give an opinion about it when given the opportunity. Therefore, when we engage skeptics we bring a biblical worldview into the conversation and create the possibility that it will be questioned.
Keep in mind that the point of the categories is not to label or categorize people, but rather to make us aware of what kind of skepticism they are expressing at the time, and therefore, what kind of conversation we are engaging.