Definiton of a category question

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The discussion clarifies the definition of identity arrows in category theory, specifically the notation id_A: A -> A, where id_A is an arrow (morphism) rather than a point. Participants emphasize that while objects can be visualized as points, arrows represent relationships between objects and cannot be conflated with the objects themselves. The distinction between arrows (morphisms) and objects is crucial, as multiple arrows can exist between the same objects, reinforcing that arrows are not subsets of sets but rather distinct entities in category theory.

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  • Understanding of basic category theory concepts, including objects and morphisms.
  • Familiarity with the notation used in category theory, particularly identity arrows.
  • Knowledge of the differences between arrows (morphisms) and relations in mathematical contexts.
  • Ability to visualize categorical structures, such as flow charts representing objects and arrows.
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  • Study the concept of morphisms in category theory to deepen understanding of their role.
  • Explore the differences between arrows and relations in mathematical frameworks.
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"for each object A there is an arrow id_A called the identity of A whose source and target are both A."

wouldnt this definition imply that id_A is a point instead of an arrow?
if not help me visualise this.

btw this should be the notation id_A:A->A
 
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Categories contain objects and "arrows" (I would call them "relations") but I've never heard of a "point" being defined for a general category.

You may be thinking of the object as a single "point" and then identifying the arrow (from the object to itself) with that "point".

Remember that in general, given two objects in a category, there may be many arrows from one to another so you cannot identify arrows with objects. In particular, there may be many arrows from a given category to itself. The arrow "id_A" is a specific one of those so you certainly cannot identify "id_A" with the object.
 
i wouldn't call them relations because a relation is generally used in reference to being some subset of the cartesian product of sets. arrows are not sets in general.
 
Objects and morphism is the usual terminology. If it helps, you can think of morphisms as arrows and objects as boxes, as in a flow chart.
 

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