Great, that helps!
First, you are correct, when the arrow looks like this:
, the sufficient is on the left, and the necessary is on the right (I tend to think of the sufficient being in front of the arrow and the necessary being after the arrow, but for now left and right will do
.
The sufficient condition is something that when it occurs, it tells you that something else has happened. So, when you know a sufficient condition has occurred, you can then follow the arrow and know that the necessary condition has also occurred (Jon and I talk about this in the lesson recap in your Online Student Center--check that out if you haven't already!).
When the necessary happens, you can't follow the arrow (since the arrow is pointing at the necessary). This is because when the necessary happens, you can't be sure that the sufficient happened (it could have, but it doesn't have to. Example: To get to the roof, you
must climb the stairs. If you climb the stairs, does that mean for sure you went to the roof? No.).
Think about the necessary condition as something that is required to be there for the sufficient to occur. When an author makes a conditional statement, he or she is saying that they believe that every time the sufficient happens, the necessary
has to happen too.
So, consider a statement like "if you are a club member, then you attended the meeting." Here we see some indicators of conditionality (if/then), and if we go to diagram it, what happens? Using what the author said and the indicators, "club member" is the sufficient (it follows "if") and "attend meeting" is the necessary (it follows "then"), leading to this diagram:
Club member
attend meeting
What does this really tell us? Well, if we see a club member, we automatically know they attended the meeting (once the sufficient was satisfied, then we followed the arrow to the necessary). What if we know someone attended the meeting? Does that mean they are a club member? No, because maybe other people were allowed to attend the meeting too (this is why the arrow in this instance points one way; you can't go backwards against the arrow).
One thing to note when doing the problems in the lesson and homework: focus heavily on indicator words for now, and don't try to "see" the sentence the way you would in the "real world." Your goal here is to understand what the
author said, not what you think is logical or should have been said. Example:
"In order to achieve world peace, everyone must eat candy."
Of course, this is a pretty ridiculous concept if you think of it in real world terms! The diagram as stated by the author is:
Achieve world peace
eat candy
Obviously, in the real world, achieving world peace does not rely upon eating candy
But, although we both know that statement is nonsensical from our perspective, our goal is simply to understand what the author said, and the diagram above properly reflects what the author said.
The nice thing about conditionality is that you are only at the start of getting into it--you'll see a lot more about this, especially because it features so heavily in Logic Games. So, if you run into trouble at first (and pretty much everyone does!), don't worry about it too much.
Please let me know if that helps. Thanks!
