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2 questions:

1. From what I understand "Only people who" is ALWAYS necessary condition indicator. Is this correct?


2. I also understand "The only" to be a sufficient condition indicator regardless of the placement in a sentence or other sufficient condition indicator in the sentence.

Ex. The only was we will win is if practice.

Diagrammed: Win->practice

Ex. Practice is the only way we will win.

Diagrammed: Win->practice

Is this right?

Be careful with your "ALWAYS." Your examples are diagrammed correctly, and generally your rules are correct, but you should be careful of sufficient-necessary conditions. If you make those phrases so black and white, you could really get tripped up when you find two conditionals that are both sufficient and necessary for the other.

Also, you can violate your second rule regarding "the only" fairly easily by phrasing a conditional strangely. For example, "If we win the only possible outcome is that they lose." Here "the only" is clearly modifying the necessary condition.

I can't think of any way to make "the only people" into a sufficient indicator right now, but it's well past my bedtime, so that might not be foolproof either. I've found that it's generally best to attack these things intuitively, possibly by substituting the conditions for something that makes sense to you so that you can better observe the logical relation.