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On Page 65 in the side bar, there is an example of the necessary condition coming before the sufficient condition. The example is as follows: To reach the top of the building, one must climb the stairs. I am very confused by this. As I understand it, the MUST indicates the necessary which would mean 'climb the stairs' is necessary and 'reach the top' is sufficient. This would NOT, then be an example fo the necessary coming first, but rather an example of it coming last. What am I missing? Please explain. Thanks!
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 Dave Killoran
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Hi Rachel,

I think you might have missed something here. Your diagram idea is correct:

  • Reach top of building :arrow: Climb Stairs

So, in the phrase "To reach the top of the building, one must climb the stairs," you'd be climbing the stairs first, right? You'd use those and walk up them to then get to the top of the building. So, "climbing the stairs," which is the necessary condition here, will chronologically occur before you reach the top of the building.

The point of the discussion here is that while all diagrams have the same basic form ( Sufficient :arrow: Necessary ), the chronology of when each condition occurs relative to the other is NOT fixed. If you look at each example there is shows different conditions happening at different times.

The reason we have this discussion is that when first faced with this form of reasoning, many student attempt to figure out which term will happen first chronologically, but that doesn't mean anything in conditionality.

And also, Robert's link above expands on this idea further :-D

Does that make sense? Please let me know.

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