The haecceity of something refers to the quality that makes it what it is: its essence. Haecceity is what makes a dog a dog or a fork a fork.

Haecceity is a fancy-sounding word for a simple concept that’s expressed well by its Latin origin, which means this-ness. Philosophers can debate the haecceity of people, meaning what it is that makes a person a person. If you're talking about what makes a chair a chair, or what makes a cat a cat, or what makes a star a star, you're discussing haecceity.

Definitions of haecceity
  1. noun
    the essence that makes something the kind of thing it is and makes it different from any other
    synonyms: quiddity
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    type of:
    center, centre, core, essence, gist, heart, heart and soul, inwardness, kernel, marrow, meat, nitty-gritty, nub, pith, substance, sum
    the choicest or most essential or most vital part of some idea or experience
Word Family

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