In my civilian life, I'm a software developer. Those who lack proficiency with computers assume that I'm something of a wizard. Alas, I do not possess any magical powers.
When you distil it down, I am paid to solve problems. I do so in a very specific way: by translating the requirements of the business into pieces of code that can be repeatedly executed by a computer.
It might seem obvious that to solve a problem, one must first define it. The business is really good at creating a wish list: they desire an application with such-and-such a set of features. But, in the midst of all of the excitement about features, they often lose sight of the problem they are trying to solve. We may end up creating an application with all the bells and whistles which nonetheless fails to meet the needs of the users.
So we find, curiously enough, that the end is a very good place to start. It is the same with ethics. Before we can determine whether something is good or evil, we must know the end to which man ought to be directed.
As obvious as this seems, that's not the way we speak about ethics. We speak not of ends, but means. If we wish to engage in a particular act, we will insist that this behavior doesn't affect anyone else. If we desire to sanction a particular act, we will appeal to some nebulous moral majority. One wouldn't want to be caught on the wrong side of history.
For our purposes, it is not essential that I posit an entire teleology. It is enough to insist that the good of man requires that he be alive. Said otherwise, his life is a good. In our decadent times, such a modest proposal might be considered controversial, but it will have to do for now.
It follows from this end that there are behaviours that are not conducive to the good of man, most obviously, suicide. Some would insist that suicide "doesn't affect anyone else." In most cases, this is a lie, but even if it were true, this behavior would still be a moral evil since it acts against the good of man.
This is the manner in which we ought to think about ethics, but it is not the way in which we do so. As a result, our discussions fail to go anywhere.
Just as it is with ethics, so too with medicine. We can only know if a pill is good if we know that it will work towards the good of man. We can only recommend a procedure if we know that it too works towards that end. Reducing fever is conducive to the end of man; terminating a pregnancy is not.
Now, there are procedures that go wrong, just as there are medicine that fail to work. This is a separate point. If the fever fails to come down, we must seek a more effective means to this end.
If we keep the necessity of the end in mind, we will improve our ability to minimize our confusion, be it in business, ethics, or medicine.