Responsibility for what one doesn’t do

In my blog last week I concluded that I cannot be held for responsible for a consequence of an action of mine if this consequence was an action done by another person, say A. The example was a thief that dropped my vase when he noticed that I came home, while I did not know that there was a thief in my house. In this case it is clear that I am not responsible. But does this mean that I am never responsible for what another person does? I think that we cannot give a general answer to this question but at least we can distinguish several cases:
a) I hadn’t foreseen the action by A and I couldn’t have foreseen it.
b) I hadn’t foreseen the action by A but reasonably I should have foreseen it.
c) I had foreseen the action by A, but A acted on his or her own initiative.
d) I had asked, ordered, forced …. A to do the action.
I shall not give examples and discuss this in detail, but I think that we can say that responsibility is a position on a gliding scale. a-d indicate a few positions on this scale from not responsible at all to very responsible. These positions can be further refined (especially d); intermediate positions can be added.
The upshot of all this is, and in fact we knew this already from daily life, that one can even be responsible for what one hasn’t done in person.