In a thread a bit ago, there was some talking about how negative and positive energy aren't inherently tied to alignments and this made me start thinking about exactly what the 2 energies actual do support and oppose.
Negative energy seems to support stagnation, as many of the creatures who "live" on it are obsessive and immortal(ghosts, ghouls, revenants, etc). It wants to kill life and stagnate a world continuously exposed to it, make something that never changes. It kind of wants to convert all life into this specific immortal non-changing ordered creatures, assimilating things slowly.
meanwhile, positive energy support life, which constantly goes through a process that makes it change to favor it's environment and thus favors and support creatures who can change. All the sentient creatures using this energy seem to vary widely in their beliefs and can even change their beliefs over time. Creatures powered by positive energy are generally not immortal and on average most creatures have life spans less than 5 years. This makes me believe that positive energy inherently favors an adapting and changing ecosystem.
Because of these, I came to the conclusion that if I HAD to hook up an alignment to the 2 energies, positive would be chaotic good, and negative would be lawful evil.
NOTE: this isn't what i believe the alignments of the energies are in the rules, just what I think they relate to the most after careful consideration.