If we were to achieve the goal of explaining all mental functions in neurobiological terms, then we must have knowledge of neurons and their basic functions, a knowledge of how neurons interact, and a delineation of the psychological faculties to be explained. Thus, we can diagram:
EMFNT ==> KNBF & KHNI & DPFE
Not DPFE or not KHNI or not KNBF ==> not EMFNT
The passage then falsely concludes that mental functions are "bound to receive explanations in neurobiological terms in the near future" (i.e. EMFNT). We know that currently there is a substantial amount of KNBF and we have DPFE (of visual perception and memory). However, we are missing one more required condition: KHNI. The passage is arguing that because we have KNBF and DPFE we can conclude EAMF is possible. However, KNBF and DPFE are parts of the overall necessary condition of the principle rule. All three of KNBF, KHNI and DPFE are required for there to be EMFNT. However, having all three does not prove the existence of EMFNT (remember DON'T JUST REVERSE!). Currently, we do not know if we have KHNI. If we do not have KHNI then according to the contrapositive, we do not have EMFNT.
It's also noteworthy to see that the principle rule states "all mental functions will be explainable in neurobiological terms" but the conclusion states "mental functions are bound to receive explanations in neurobiological terms in the near future." Just because we can explain mental functions in neurobiological terms, doesn't necessarily mean that we will.
(A) is incorrect because the conclusion does not contradict the claim of the physicalists. The wording of the conclusion even states, "as the physicalists claim," showing that the physicalists' claim goes a long with the conclusion.
(B) is incorrect because not knowing exactly what is known about the basic functions of neurons is not an error in reasoning here. The passage stated that achieving the goal requires knowledge of neurons and their basic functions. That is all we need to know. Since the passage doesn't go deeper into what specifically we must know to guarantee achieving the goal, it is not necessary for the argument.
(C) is incorrect because the word "neurobiological" was not used in the same meaning as "mental." It is clear that we want to explain mental functions in neurobiological terms. Thus, the two terms are not used as though they had the same meaning.
(D) is incorrect because the usefulness of explaining mental functions in neurobiological terms is irrelevant. The argument states that the goal is to be able to explain all mental functions in neurobiological terms. Whether that is useful or not is of no importance to us. We merely want to see what the error in reasoning of the argument is, which is not knowing whether or not we have a knowledge of how neurons interact.
(E) is CORRECT because we need to know whether or not we have a knowledge of how neurons interact. Because if we do not have this knowledge, then, as we can see by the contrapositive of the principle rule, we will not be able to explain mental functions in neurobiological terms, since it is required.
Hope that was helpful! Let me know if you have any other questions.
