Consider the following premises. p_2 -> p_15. ~p_15. q_15 -> p_4. p_15 <-> q_15. p_4 -> p_2. Can we infer p_2 from them?
 From p_15 <-> q_15 we can infer p_15 -> q_15. From q_15 -> p_4, p_4 -> p_2 we can infer q_15 -> p_2. From p_15 -> q_15, q_15 -> p_2 we can infer p_15 -> p_2. From p_2 -> p_15, p_15 -> p_2 we can infer p_2 <-> p_15. Finally, from p_2 <-> p_15, ~p_15 we can infer ~p_2, which contradicts p_2. Therefore, the answer is no.