Consider the following premises. For all x_6, x_6 is a doctor or x_6 is a server. There is at least one x_6 for which x_6 is a taxi driver. For all x_6, if x_6 were a server, then x_6 is climbing a mountain. For all x_6, if x_6 were a doctor, then x_6 is climbing a mountain. Can we infer the following from them? For all x_6, x_6 is not a taxi driver.
 From the fact that for all x_6, if x_6 were a doctor, then x_6 is climbing a mountain, that for all x_6, if x_6 were a server, then x_6 is climbing a mountain, and that for all x_6, x_6 is a doctor or x_6 is a server we can infer that for all x_6, x_6 will climb a mountain. From the fact that for all x_6, x_6 will climb a mountain, and that there is at least one x_6 for which x_6 is a taxi driver we can infer that there is at least one x_6 for which x_6 will climb a mountain and x_6 is a taxi driver. Finally, from the fact that there is at least one x_6 for which x_6 will climb a mountain and x_6 is a taxi driver we can infer that there is at least one x_6 for which x_6 will climb a mountain, which contradicts that For all x_6, x_6 is not a taxi driver. Therefore, the answer is no.