Final answer:
The division into 2 mutually exclusive or contradictory ideas is called a dichotomy, which refers to fundamentally opposed concepts or entities, and should not be confused with a false dichotomy, an informal fallacy that presents limited options without proper justification.
Step-by-step explanation:
The division into 2 mutually exclusive or contradictory ideas is known as a dichotomy. This concept refers to a pair of concepts or entities that are portrayed as being completely opposite or fundamentally different from one another. It is often presented as two options which seem to be the only possibilities. This kind of division is evident in various arguments and philosophical discussions, for example, the contrast between free will and determinism, or physical and spiritual substances in dualism. The dichotomy can sometimes lean towards a false dichotomy, which is an informal fallacy where only a limited set of options are presented, without justification, when more possibilities exist. The law of the excluded middle in logic underlines a related principle stating that for any particular proposition, either that proposition or its negation must be true, but this law does not imply that only two alternatives exist in broader contexts beyond formal logic.