A potential response is that one may proceed in Trolley but not in Transplant. The key difference can be explained by the Kantian idea of using people as an end in itself, rather than a means. In essence, for an agent to proceed in Transplant, he physically needs the body of a healthy man in order to save the five; whereas in Trolley the bystander does not use his victim in any sense (Thompson, Reading B). While this idea explains Trolley and Transplant in its vanilla form, it fails to explain the permissibility of pulling the lever in the loop variant (Thompson, Reading B) where one must be used or the five will die.
The doctrine of double effect is a principle which states that an action which is morally impermissible if done intentionally, may be permissible if it only brought about as a foreseen consequence of promoting an ultimate good end (Study Guide p. 42). In the case of Transplant, the doctrine may explain the outcome of saving the five but fails to explain the means of doing so. If the organs were obtained by a means where the agent did not intentionally kill a person, then the doctrine may be able explain this. However in order to save the five, an agent must kill the one, and therefore it is implausible to state that the intentional murder of an innocent to achieve an end can be passed off as a foreseen consequence.
Thompson’s explanation on the permissibility of proceeding in Trolley relates to the histories of how each person came to be where they are on each track (Thompson, Reading C), whereas a preference utilitarian view relates to the maximisation of utility by fulfilling preferences (Study Guide p. 13). Thompson states that at the beginning of Trolley (i.e. early morning), there is a time where it is in the best interests of all track-workers for the Trolley to be diverted onto the lone worker. At this time, Thompson notes that, provided positions have not yet been made by the lot, the probability of every track-worker surviving the incident is greater if the trolley is diverted than if the trolley is not (Thompson, Reading C) (Study Guide p. 29). A preference utilitarian explanation of why it is permissible to pull the lever stems from the value of satisfying as many individual preferences as possible. In this view, pulling the lever would lead to the greatest overall utility as the preference to live of the five all outweigh the preference to live of the one. In the same vein, the preferences of the one that are disrupted will be of less relative value than if the preferences of the five are disrupted.