Question
Determine the validity of the following arguments using the direct method of truth table:
$\sim A\ v \sim B$
$\sim A$
$\therefore\ \sim B$

Answer

Combining the two bases of this argument as a whole, the argument will be as follows:
$(\sim A\ v \sim B)\ \&\ \sim A$
$\therefore\ \sim B$
Truth Table:
  Support Statement The resulting statement
  $1$ $2$ $3$ $4$ $5$ $6$ $7$
$A$ $B$ $\sim A$ $\sim B$ $\sim A v \sim B$ $(\sim A\ v \sim B)\ \&\ \sim A$ $\sim B$
$1$ $T$ $T$ $F$ $F$ $F$ $F$ $F$
$2$ $T$ $F$ $F$ $T$ $T$ $F$ $T$
$3$ $F$ $T$ $T$ $F$ $T$ $T^*$ $F^*$
$4$ $F$ $F$ $T$ $T$ $T$ $T$ $T$
  $1(\sim )$ $2(\sim )$ $3, 4(v)$ $5, 3(\&)$ As $4$
Judgment of the validity of the argument: In the truth table above, seven full columns have been formed. In which the column no. $6th$ base statement and column no. $7$ is the introduction of the result statement. Row out of the total four rows of the truth table. The base statement truth in $3$ and $4$ is $‘T’.$ But of the row. The result in $3$ is the false $‘F’.$ Hence this argument is disproportionate.

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