Follow-up to this. If I can't control, but can influence, events, am I partially responsible for the result? Control, of course, requires being able to alter something entirely at one's will. I control the mouse if I can move it where I please. Influence, on the other hand, is more subtle: something more like potential redirection by exerting indirect forces. So, I can't control the cursor on the screen (I can't move it at my will), but I can influence it through the mouse or the keyboard or other control device.
So far, so good. Now, if control is necessary for responsibility, since influence is not control, it follows that influence does not convey any responsibility. But, if control is only sufficient for responsibility, then it could be that influence is also sufficient.
If control is sufficient, then there is very little I have any responsibility for. It's rare for me to be able to redirect anything entirely at my will, particularly other persons.
But, if control were sufficient, then I'd think that influence should not be. After all, we can influence just about anything, to some minimal degree. (Think of the butterfly flapping its wings and causing a hurricane.) So, there'd need to be an account that could rule out influence as also being sufficient, which I think could be done by setting a minimum threshold of influence. That is, one would have to be able to exert a certain amount of influence before one could be held responsible.
If we were to set a minimum threshold for influence, though, why not just call anything that rose above this threshold "control"? That is, we'd end up relaxing the idea of "control" to allow it to apply to cases where we can exercise significant potential redirection by exerting indirect forces (and allow the cases where we can dictate redirection at will to be limiting cases).
In summary, then, if control is sufficient, then the definition of control needs revision; if control is necessary, then we're very rarely responsible. The latter result is disastrous; the former not so much. If influence is sufficient, however, we also end up in disaster. So, influence cannot be sufficient, but may be necessary, and control must be relaxed to allow some sort of indirect redirection.