IMC, Detect Evil/Good/Law/Chaos locates descriptors, not intentions. Descriptors are granted by Sponsorship, not Conduct -- though most Sponsors place restrictions on Conduct, you won't get Sponsorship through Conduct alone.
Examples which I hope will clear things up:
- Human (by default) -> Weakly Good
- Vampire, Wight, Ghoul (by default) -> EVIL
- Skeleton, Zombie -> Weakly Evil
- Human Paladin -> GOOD, LAWFUL
- Human Serial Killer -> Weakly Good
- Human Priest of Evil God -> EVIL
- Quasit Familiar of CE Necromancer -> CHAOTIC, EVIL
- Quasit Familiar of CG Alienist -> CHAOTIC, EVIL
- Innocent Golden-Haired Child under the effect of Protection from Good -> EVIL
- Vampire Priest of LG God -> Murky, indistinct (I'm not saying this could happen IMC, but that's how I'd rule it)
So, a wicked merchant who cheats, lies and kills but does not have Diabolic or Demonic sponsorship will detect as Weakly Good (default Human, powered by Positive Energy), while a noble barbarian who helps orphans but has magical powers due to a pact with a Demon-Prince will detect as Weakly Evil or EVIL, depending on the strength of the pact.
D&D is a world of black-and-white morality, so I like to have clear boundries as to what are OBJECTIVELY Good & Evil actions.
-- N