Useful philosophy must be grounded in life. Although we like to believe we are at our best when disembodied consciousness, we are at base animals. Any attempt at various branches of philosophy like ethics or social interaction must recognize that.
Since before Darwin, we have understood that the primary drive of all life is to survive. That necessity is closely followed by the need to replicate. Before all else, humans are alive. Following classic logic, then, all humans seek to survive.
Uniquely, we are able to sublimate survival instincts to larger concepts. A bear may instinctively fight to the death to save her cubs, but people are able to give their life to intangible concepts like family, country, honor, and so forth in the hope that by sacrificing the individual the concept itself will continue.
Philosophy must recognize the innate power of the will to survive _ if not as an individual then as a concept. Note that that in no way constrains the actual shape of the concept. People die for evil as well as good, but nonetheless they are willing to die.
Somewhere in the foundation of a useful philosophy is the bedrock that an individual seeks to survive. Even if that drive can be warped to near invisibility.