Consider the following premises. For all x_12, x_12 is a doctor if and only if x_12 will play squash. For all x_12, x_12 will not go running. There is at least one x_12 for which x_12 is a doctor if and only if x_12 will go running. Can we infer the following from them? There is at least one x_12 for which x_12 will not play squash.
 From the fact that for all x_12, x_12 is a doctor if and only if x_12 will play squash we can infer that for all x_12, if x_12 plays squash, then x_12 is a doctor. From the fact that there is at least one x_12 for which x_12 is a doctor if and only if x_12 will go running, and that for all x_12, x_12 will not go running we can infer that there is at least one x_12 for which x_12 is not a doctor. Finally, from the fact that for all x_12, if x_12 plays squash, then x_12 is a doctor, and that there is at least one x_12 for which x_12 is not a doctor we can infer that there is at least one x_12 for which x_12 will not play squash. Therefore, the answer is yes.