$2$

$1.$ Explain what it means for a sentence A to be a logical consequence of a set of sentences $\{$$1,...,$n$\}.$

Using your definition of logical consequence, explain what it means for an argument with the

following structure to count as a valid argument. $(4$ marks$)$

m

n

$2.$ Indicate which of the following strings of symbols count as sentences in the language of truth

functional logic we are working with in class. $(6$ points$)$

$$P $$Q $$P $$ Q $[($P $$ Q$)$ Q$]$P

$($ $$ $)($ $$$)$ $1,...,$n $$ A

$$S $$ T