Moral influence means persuading another that one can make that other more uncomfortable than that other can make oneself.
 Samuel Butler, The Note-Books of Samuel Butler (1912). copy citation

Context

“It makes a worse face and raises itself up on its haunches. I stand and look. It jumps down from its shelf and makes as if it intended to go for me. I move back. The caracal has exerted a moral influence over me which I have been unable to resist. Moral influence means persuading another that one can make that other more uncomfortable than that other can make oneself. Mental and Physical Pabulum When we go up to the shelves in the reading-room of the British Museum, how like it is to wasps flying up and down an apricot tree that is trained against a wall, or cattle coming down to drink at a pool!” source