¬A → B , ¬B ⊢ A

Question

1. not A > B :PR
2. not B :PR

PR = Premises This is the strategy of the Conditional Introduction. On line 3 I'm assuming the antecedent of my goal sentence.

(You don’t have to use this vv but it’s what I’m using for class.)

Conjunction Introduction - /\Im,n Conjunction Elimination - /\Em Disjunction Introduction - /Im Disjunction Elimination - /Em,n-o,p-q Conditional Introduction - ->Im-n Conditional Elimination - ->Em,n Biconditional Introduction - <->Im-n,o-p Biconditional Elimination - <->Em,n Negation Introduction - ~Im-n Negation Elimination - ~Em,n Explosion - Xm Indirect Proof - IPm-n Disjunctive Syllogism - DSm,n Modus Tollens - MTm,n Double Negation Elimination - DNEm

Answer 1

On line 3 I'm assuming the antecedent of my goal sentence.

Rather, assume $\lnot A$, which is the negation of your goal sentence, so that you can produce a proof by reduction to absurdity.