Total responsibility.
I don't think that anyone is excused for sinning just because someone else sins as well.
Here is the difference.
1. A man sees a perfectly modest woman and lusts after her. The Man alone is at fault.
2. The same man sees an immodest woman, and lusts after her, they are BOTH at fault.
3. The Man sees an immodest woman turns his attention away from her and goes on about his day. Only the woman has sinned.
Is that what you were looking for?
Good answer but not quite what I was looking for, let me ask the question a different way using Allen's example.
Cain asked the the same thing to God when God asked where Able was??
"Am I my brothers Keeper?" Am I responsible for looking after him??
Let me turn this around a bit. Did Able's actions provoke Cain to sin?
Able certainly knew that God was pleased with him and yet not pleased with Cain.
Ge 4:8And Cain told Abel his brother. And it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.
Now, we're not told exactly what Able's response was but it we are told that he went on to work and time passed. During this passing of time, something Able did or didn't do (or say), allowed Cain's anger to fester and eventually led to the sin of murder.
Now, can it be said that the stonger "Christian" caused the weaker brother to stumble?
Dale is correct in that we are totally responsible for our own actions. But I'm more interested that folk know WHY we are responsible. I'm tired to death of being told that every little thing I do may cause someone to stumble, but I read the passage in a different light.
My take on the entire passage is that we do nothing to intentionally make a weaker brother to stumble.
Ro 14:21It is good not to eat flesh, nor to drink wine, nor [to do anything] whereby thy brother stumbleth.
This verse implies knowledge of the brother's struggle. Anything more causes us to feel as though we MUST at all costs be perfect, when we know perfection is something we are working toward but won't be accomplished until the next life. Attempts to be perfect, lead eventually into to legalism and lists of manmade rules in order achieve perfections without the understanding that it is not our own perfection that pleases God, but Christ's perfection within us that pleases God.