Logical Reasoning Drill Clarification

[OlgaC881]

Hello Manhattan,

I had a clarifying question about the Chapter 4 Drill: Conditional Logical Chaining Flaws on page 134. In the second example, the flawed statement "It's clearly Sunday: Whit has on his Broncos jersey" is documented as J ---> S implying that the condition that has occurred is that Whit is wearing his Broncos jersey and we are extrapolating that it is Sunday. I was under the impression that the colon can be read as "thus" or even "then" so I was confused as to why "S" is the necessary condition instead of "J".

Thank you in advance!

[dmitry]

Generally, a colon means that whatever follows is equivalent to, or an example of, what came before. So if I make an assertion followed by a colon, whatever comes next should clarify what I mean or why I thought so.

He is very stingy: he wouldn't even give his mother a dime.
The day was unproductive: mostly we just lay around eating chips.

Notice that these two cases don't quite translate to conditionals. We're not saying "Won't give mother dime --> stingy" (although that seems true) or "Lay around --> unproductive." We're just mentioning specific cases that occurred. The difference in our Whit example is that we have conclusion language ("It's clearly Sunday") followed by our clarifying statement (jersey on). So in cases like that, we do have Nec:Suff structure. Following the little cue words is important. The first part has conclusion language ("clearly"), while the second just states a fact. Here's another example:

My neighbor must be very political: her whole yard is covered in signs.

We have a conclusion ("must be") followed by evidence. So could we use different language to switch the order? Probably not with a colon, because a conclusion can't really clarify a premise, so we'd probably see a semicolon:

My dog is barking like crazy; someone must be at the door.

Note that if we switched the order of those clauses, a colon would work just fine. I hope this helps!