I do not believe there is a way to logically bridge this gap. Any attempt at justification will ultimately devolve into an infinite regress, circular logic, or a fundamental choice/premise that cannot itself be justified. Given these options, my position will start from the choice to live. More specifically, it will start from that choice, assuming that certain other conditions (values) are satisfied. The specifics of those conditions will vary from person to person due to differences in personality, but the analysis following their selection should not. In other words, the fundamental question that ethics must address is how to realize the selected values. The answers are the virtues: rationality, courage, etc.
As applied to other people, this requires acknowledgment of the fact that it would be contradictory to treat others as a means to an end while at the same time expecting them to treat you as an end. They require the same freedom of action to realize their goals as you do. Success for either of you is not guaranteed, however. This leads to the distinction between negative and positive rights which I will address in my next post on politics. For now, it is sufficient to note that there is generally no ethical duty to assist others. Such a duty would have no logical limit and could only lead to self-destruction. All of this applies to relationships with humanity at large. To the extent that you value certain individuals, helping them does not constitute a sacrifice so long as your commitment is commensurate with their value to you.
Inner Questions 