A term originally coined on rec.games.frp.advocacy and included in the Threefold Model, which was later used by GENder Theory and the GNS Model. In the original Threefold, it is defined as the style which values resolving in-game events based solely on game-world considerations, without allowing meta-game concerns to affect the decision. This means an exploratory act where you create elements in the game and see what they lead to rather than deciding on the basis of other components.

It was similarly defined in Ron Edwards' early essay "System Does Matter" as "This player is satisfied if the system "creates" a little pocket universe without fudging."In Scarlet Jesters' GENder the category of "Simulationism" was renamed "Explorationism" and defined as prioritizing Exploration. Ron Edwards adopted this definition for GNS on The Forge. For the original GNS essay, he defined it similarly by exploration, with an alternate term as prioritizing "The Dream".

Later, other definitions were suggested. Ralph Mazza (aka Valamir) suggested Simulationism as attempting discovery, exploring "what if". Jay Willis (aka Silmenume) suggested that Simulationism was Bricolage with the goal of creating myth. Ron Edwards, who had originally defined the GNS terms, suggested an alternative definition based on validation of input, likening Simulationism to celebration (see Celebration) and later coining the phrase "constructive denial."

References:

• The Threefold Model FAQ (rgfa, Oct 1998)
• GNS and Other Matters of Role-playing Theory (The Forge, Oct 2001)
• Simulationism: The Right to Dream (The Forge, Feb 2003)
• Threefold Simulationism Explained (Jan 2004)
• The Model as seen by Valamir (The Forge, Jul 2004)
• What GNS Is About (The Forge, Aug 2004)
• Referee/Player Sim/Nar Clash (The Forge, Sep 2004)
• Validation of Input in Sim (The Forge, Oct 2004)
• Sim is Bricolage and makes myth - comments? (The Forge, Jan 2005)