Nevertheless—this is the fourth and final problem—sufficient means may be superfluous to an end, where this means something like that, even if those means were omitted, the end would still be achieved.  Suppose that Drug 1 is a sufficient means to relieving the patient’s pain.  A doctor is sure to give Drug 1.  Giving Drug 2, in addition, would at first neutralize the effect of Drug 1, but then recombine with it to produce a third drug, which will relieve the patient’s pain.  Giving Drug 2 would be superfluous to relieving the patient’s pain, although it would help to bring it about, by being part of the cause of the relief of the patient’s pain.  Does the doctor then also have any reason to give Drug 2?  At first, one might be tempted to say that the doctor does indeed have reason to give Drug 2, but that this reason is outweighed by the cost of giving Drug 2.  But observe that no matter how low we make that cost, it still outweighs any reason to give it.  This suggests that there is no reason at all to give it. Note that necessary means cannot be superfluous, since if necessary means were left out, the end would not be achieved.