When working out what should guide public institutions and policies in our lives and human communities, those who chime in from ancient to contemporary times have advanced various proposals and they have often been divided into two groups. Members of one of these advance certain basic principles that ought to ground the institutions and policies, while those of the other suggest that the way to decide is by focusing on the anticipated consequences, never mind any purportedly firm principles (which tend, in any case, to become obsolete or misapplied).
In the United States and in other developed countries the former group is called deontologists while the latter consequentialists. (In the history of political ideas Immanuel Kant is deemed to be the quintessential deontologist while John Stuart Mill the most prominent consequentialist.) Deontologists try to identify principles by which we ought to live and guide our public affairs – for example, a set of basic rights everyone supposedly has and which may never be violated; this will, argues the deontologist, insure justice and other good things in community affairs. For the consequentialist the idea that should govern is whether some policy most effectively promotes what is desirable – for example, spend whatever is necessary so as to eliminate poverty and sickness, never mind if anyone's rights are violated in the process since those rights mostly tend to be obstacles to what needs to be done.
Is this a good, useful distinction? I have my doubts. For one, no one can tell for sure what the result or consequence of a course of action or public policy will be down the line, not certainly in any detail. And when it is possible to tell, it is because we have discovered that following some principle is likely to bring forth a given result. The actual actions or policies are not available for inspection until after they have been tried. So if we are to be guided by anything, it cannot be the results, which lie in the future and are mostly speculative. It would have to be certain rules or principles that we have found to be helpful in the past when we deployed them.
On the other hand, principles are always limited by the fact that they were discovered during the past that may not quite be like the present and future or, even more likely, the scopes of which are limited by what we know so far. Thus, for example, take the U.S. Constitution that contains a set of principles (especially in the Bill of Rights). It is subject to amendments in part so as to update these principles in light of new knowledge and new issues in need of being addressed. Once amendments are seen as possible, even necessary, strict reliance on the principles is admittedly hopeless.
So then what about the two kind of approaches, deontological versus consquentialist? Neither is really adequate to what human beings need to guide their lives. Yes, they will have to identify certain ethical, political, legal and other principles – e.g., in medicine, engineering, or automobile driving – but once they have done so they will still need to keep vigilant so as to make sure they aren't missing some good reason for updating these. However, focusing entirely on the consequences of their actions and policies will not do the job either since those are not yet here to deal with. They will have to ease up to them with the help of the principles, more or less complete, that they have found to be soundly based on their knowledge of the past.
Fortunately, although our knowledge is rarely complete – and never final – about anything that surrounds us in the world, the world itself tends to be fairly steady and predictable (once one has studied it carefully, without bias or prejudice such as wishful thinking). It is not possible to escape the need to balance reasonably well established principles and expected consequences. With these in hand, many of our tasks and challenges are likely to be managed pretty well although we need also to be prepared for surprises. There is no substitute for paying close attention.