Sociology teaches us to look at the world from different perspectives (sides). It is not only our perspectives that are important, but also the perspectives of others. From each viewpoint, we see only a part of the whole. In short with just one perspective we will not get a full picture of the world.
When we compare the different views of people about the world, we get a reasonable picture of the entire thing. Each viewpoint of others tells us what is hidden from our own viewpoint.