"It resembles a pair of shears, so joined that they cannot be separated, often moving in opposite directions, yet always punishing anyone who comes between them"

This quote by Sydney Smith is a metaphor for two opposing forces that are inextricably connected. The image of a set of shears indicates that these 2 forces are powerful and sharp, and that they are so intertwined that they can not be separated. The idea of them moving in opposite instructions suggests that these two forces are in constant dispute, yet they are unified in penalizing anybody who gets in between them. This might be analyzed as a cautioning to stay away from the conflict in between these two forces, as it is dangerous to get involved. It could also be viewed as a suggestion that even when two forces remain in opposition, they can still be unified in their function.