How to write out the logic that justifies this conclusion? Forum

[ScottRiqui]

I'm used to drawing a conclusion from symbolic logic when the rules make a nice "chain", but even though I think the following conclusion is valid, I don't get a chain when I draw out the logic. Is my conclusion flawed, is the symbolic logic incorrect, or should I not be expecting to be able to form a "chain" from the statements given?


"Everyone who participated in the field trip was a student. Some of the field trip participants got lost. Therefore, some students got lost."

FT -> S
FT some L
-----------
S some L


There's not a "chain" in the typical sense, but does the first rule allow me to simply replace FT with S in the second rule, giving me the conclusion?

[KFV]

Yes, exactly.

FT -> S can really be broken down into two statements:

F=S
~S=~F

(the equal signs only work left to right of course)