Haecceity
Haecceity (; from the Latin haecceitas, ‘thisness’) is a term from medieval scholastic philosophy, first coined by followers of Duns Scotus to denote a concept that he seems to have originated: the irreducible determination of a thing that makes it this particular thing. Haecceity is a person’s or object’s thisness, the individualising difference between the concept “a person” and the concept “Socrates” (i.e., a specific person). In modern philosophy of physics, it is sometimes referred to as primitive thisness.
Words for “haecceity” include thisness, individuality, and suchness, which all point to the unique, non-qualitative property that makes an individual thing what it is. In contrast to a thing’s quiddity (its “whatness” or essence), haecceity refers to its “thisness,” or why it is a specific individual entity. Other related terms include individual essence and intrinsic mode.
| Term | Explanation |
|---|---|
| Thisness | The most direct English translation and synonym for haecceity, coined by the poet Gerard Manley Hopkins. It refers to the unique properties that make a specific entity a distinct individual. |
| Individuality | A general term for the quality or state of being individual and distinct from others, which haecceity aims to explain. |
| Suchness | A term sometimes used in recent philosophy to describe the non-qualitative property of an individual, similar to the scholastic concept of haecceity. |
| Quiddity | The “whatness” of a thing, or its essence. Haecceity is the “thisness” of that thing, which is distinct from its defining characteristics (quiddity). |
| Individual essence | A modern term used in analytical philosophy, which can encompass both the scholastic haecceity (individuation) and the quiddity (essential properties) of an individual. |
| Designated singularity in particular | A descriptive phrase used to help conceptualize haecceity as the specific, unique quality that makes a particular entity a singularity. |
| Intrinsic mode | A term used in some philosophical contexts to describe haecceity as a property of a thing that is intrinsic to it, but not a qualitative one. |
AI responses may include mistakes.
[1] https://plato.stanford.edu/archives/fall2025/entries/medieval-haecceity/
[2] https://fiveable.me/key-terms/introduction-christianity/haecceity
[3] https://www.merriam-webster.com/dictionary/haecceity
[4] https://plato.stanford.edu/archives/win2015/entries/medieval-haecceity/
[5] https://pmc.ncbi.nlm.nih.gov/articles/PMC3693789/
[7] https://www.imaginativeuniversal.com/blog/2009/03/03/haecceity/
Haecceitism is a philosophical concept that stems from the field of metaphysics, particularly dealing with the nature of individuality and identity. The term “haecceity” itself comes from the Latin word “haecceitas,” which means “thisness.” This concept was originally developed in the medieval scholastic tradition and is often associated with the philosopher John Duns Scotus.
In essence, haecceitism focuses on the idea that each individual entity has a unique, unrepeatable quality that makes it different from every other entity. This quality is not dependent on an entity’s properties or relations to other things; it’s something intrinsic to the entity itself, which is “a set of principles which are essential to it and distinguish it from everything else.” James Ladyman characterizes haecceitism as “the claim that worlds can differ solo numero, that worlds can differ de re whilst not differing de dicto, sometimes said, that worlds can differ solely by the permutation of individuals.”
For example, consider two completely identical twins. Even if they share all the same properties (like appearance, genetic makeup, etc.), haecceitism holds that there is still something fundamentally different about each twin that makes them distinct individuals. This difference is their “haecceity.”
Haecceitism challenges the idea that an individual can be fully described or defined by its properties or relations. Instead, it suggests that there is an irreducible aspect to each individual that makes them uniquely themselves. This concept has implications for discussions about identity over time, the nature of individual objects, and the idea of identity of indiscernibles in philosophy.
In more modern contexts, haecceitism is sometimes discussed in relation to issues of the nature of transworld identity in metaphysics. It raises questions about how we recognize and understand the individuality of objects, and about what it is that makes something the particular thing it is.