Included Middle is an idea proposed by Stéphane Lupasco (in *The Principle of Antagonism and the Logic of Energy* in 1951), further developed by Joseph E. Brenner and Basarab Nicolescu, and also supported by Werner Heisenberg. The notion pertains to physics and quantum mechanics, and may have wider application in other domains such as information theory and computing, epistemology, and theories of consciousness. The Included Middle is a theory proposing that logic has a three-part structure. The three parts are the positions of asserting something, the negation of this assertion, and a third position that is neither or both. Lupasco labeled these states A, not-A, and T. The Included Middle stands in opposition to classical logic stemming from Aristotle. In classical logic, the Principle of Non-contradiction specifically proposes an Excluded Middle, that no middle position exists, *tertium non datur* (there is no third option). In traditional logic, for any proposition, either that proposition is true, or its negation is true (there is either A or not-A). While this could be true for circumscribed domains that contain only A and not-A, there may also be a larger position not captured by these two claims, and that is articulated by the Included Middle.

Heisenberg noticed that there are cases where the straightforward classical logic of A and not-A does not hold. He pointed out how the traditional law of Excluded Middle has to be modified in Quantum Mechanics. In general cases at the macro scale, the law of Excluded Middle would seem to hold. Either there is a table here, or there is not a table here. There is no third position. But in the Quantum Mechanical realm, there are the ideas of superposition and possibility, where both states could be true. Consider Schrödinger’s cat being possibly either dead or alive, until an observer checks and possibility collapses into a reality state. Thus a term of logic is needed to describe this third possible situation, hence the Included Middle. It is not “middle” in the sense of being between A and not-A, that there is a partial table here, but rather in the sense that there is a third position, another state of reality, that contains both A and not-A. This can be conceptualized by appealing to levels of reality. A and not-A exist at one level of reality, and the third position at another. At the level of A and not-A, there are only the two contradictory possibilities. At a higher level of reality, however, there is a larger domain, where both elements could be possible; both elements are members of a larger set of possibilities.

Included Middle is a concept already deployed in a variety of scientific domains and could benefit from a wider application in being promoted to “meme” status. This is because beyond its uses in science, Included Middle is a model for thinking. The Included Middle is a conceptual model that overcomes dualism and opens a frame that is complex and multi-dimensional, not merely one of binary elements and simple linear causality. We have now come to comprehend and address our world as one that is complex as opposed to basic, and formal tools that support this investigation are crucial. The Included Middle helps to expose how our thinking process unfolds. When attempting to grasp anything new, a basic “A, not-A” logic could be the first step in understanding the situation. However, the idea is then to progress to the next step which is another level of thinking that holds both A and not-A. The Included Middle is a more robust model that has properties of both determinacy and indeterminacy, the universal and the particular, the part and the whole, and actuality and possibility. The Included Middle is a position of greater complexity and possibility for addressing any situation. Conceiving of a third space that holds two apparent contradictions of a problem is what the Included Middle might bring to contemporary challenges in consciousness, artificial intelligence, disease pathologies, and unified theories in physics and cosmology.