The same way you would any other type of Pokemon. If you are playing Pokemon XD, have it facing another ghost type in the Purification Chamber. If you are playing Colosseum or haven't unlocked/don't use the Purification Chamber, just keep battling with it and purify it the normal way.
Of course, if this question isn't trivial, and you're just wondering why a malicious type of Pokemon such as the ghost type can be purified, then I'm not sure.
I believe Dark and Ghost types are weak against Ghost types. Ghost types may not be, but I think they are.
Ghost types are fundamentally weak against ghost or dark attacks.
When attacking, Ghost-Type Pokémon are strong against Psychic-Types and other Ghost-Types, weak against Dark-Types and Steel-Types, and useless against Normal-Types. When being attacked, Ghost-Type Pokémon are strong against Bug-Types and Poison-Types, weak against Dark-Types and other Ghost-Types, and invincible against Normal-Types and Fighting-Types (barring the use of a move like Foresight).
The pokemon that are strong against psychic are bug, dark, and ghost.
the answer is the . . . . . . . . . . . . . . . . A B R
you can't, in order to purify it you must put it in the purify chamber around 4 regular Pokemon and get a full tempo to get a full tempo you must arrange the Pokemon in a way that they beat each other, EXAMPLE: put 4 ghost types in a circle and you will get full tempo cause ghost beats ghost. Now if you do that to the other 8 sets lugia will be able to become purified.
Purify it's soul by calming it's spirit. The ghost always has some sort of regret which is why it's there.
the ghost types areYAMASKCONFAGRIGUSFRILLISHJELLICENTLITWICKLAMPENTCHANDELUREGOLETTGOLURK
I believe Dark and Ghost types are weak against Ghost types. Ghost types may not be, but I think they are.
Ghost types are fundamentally weak against ghost or dark attacks.
When attacking, Ghost-Type Pokémon are strong against Psychic-Types and other Ghost-Types, weak against Dark-Types and Steel-Types, and useless against Normal-Types. When being attacked, Ghost-Type Pokémon are strong against Bug-Types and Poison-Types, weak against Dark-Types and other Ghost-Types, and invincible against Normal-Types and Fighting-Types (barring the use of a move like Foresight).
The pokemon that are strong against psychic are bug, dark, and ghost.
the answer is the . . . . . . . . . . . . . . . . A B R
Ghost-Type moves are strong against Psychic-Types and other Ghost-Types. Ghost-Type Pokémon are strong against Poison-Types and Bug-Types, and particularly strong against Normal-Types and Fighting-Types, since they don't affect Ghost-Types.
Ghost types are weak against Dark and Ghost type moves.
I'm afraid there are no types of pokemon that can beat the Ghost type :P
Dark, and ghost.