To support conditional elements like "not" (which will be covered later on), there is a need to "seed" the engine with something known as the "Initial Fact". This fact is a special fact that is not intended to be seen by the user.

On the first working memory action (assert, fireAllRules) on a fresh working memory, the Initial Fact will be propagated through the RETE network. This allows rules that have no LHS, or perhaps do not use normal facts (such as rules that use "from" to pull data from an external source). For instance, if a new working memory is created, and no facts are asserted, calling the fireAllRules will cause the Initial Fact to propagate, possibly activating rules (otherwise, nothing would happen as there area no other facts to start with).