The principle of Symmetry put forward by David Bloor is one of the basic principles of scientific sociology of knowledge. Bruno Latour has launched an attack on relativism in David Bloor’s principle of Symmetry from the perspective of role?network theory. But his criticism falls into pluralism and opportunism. While we attempt to eliminate absolutism by relativism of the principle of Symmetry, we need to guard against the problem of relativism and the trap of pluralism and opportunism.