"There are only two kinds of people in the world: those who divide everything into two categories, and those who don't."
— Mervyn Alquist
When a cosmology is dualist, it is centered around two parts opposing each other. It can manifest as a good and an evil deity clashing, or two zealous crusading gods both convinced they are right and the other is wrong. It might have amoral jerkasses fighting over some trivial matter as their human pawns suffer and die.The two opposing sides need not even be sentient, as both the Light and Dark Side of the Force can attest. All that is required is that there are two sides and they are opposed to each other.
Note that in some philosophies, this conflict is not necessarily a existential struggle. Some opposing forces or concepts can co-exist; there is tension between them, to be sure, but the philosophy teaches to keep them both in balance.
The classic D&D alignment system is based on two sets of opposing dualities; that of Good vs. Evil and that of Order vs. Chaos.
- Good and Evil
- Order and Chaos
- Light and Darkness
- Yin and Yang
- Male and Female
- Matter and Spirit
- Positive and Negative
- Heads and Tails
- Cats and Dogs
Where more than two powers are required for worldbuilding, consider either a genuine polytheism, using the various classical elements as power centres or invoking Angels, Demons and Squid, depending on preference. Any of these can lead to values dissonance by way of either grey and grey morality or the full on orange and blue version.
Game and Story Use
- A classic fantasy theme is to have the PC's fighting for one side or the other in such a cosmic struggle.
- The RPG In Nomine might be the ultimate expression of this theme.
- A related theme is to have them caught between the two opposing forces
- As in Michael Moorcock's hero Elric
- An NPC Holy Man might subscribe to a dualistic philosophy and interpret the people he meets and the world around him in terms of the Cosmic Struggle between Truth and Falsehood.
- "Powerful you have become, the Dark Side I sense in you."
- The equally traditional subversion is to inject plenty of grey into the campaign's morality and leave the dualism as a bad habit of dangerous fanatics (<Obi-Wan>: "Only a Sith deals in absolutes" <Everyone else>: "huh?").