Definition df-id 4767

Description: Define the identity relation. Definition 9.15 of [Quine] p. 64. (Contributed by SF, 5-Jan-2015.)

Assertion

Ref	Expression
df-id	|- _I = {<.x, y>. | x = y}

Distinct variable group:   x,y

Detailed syntax breakdown of Definition df-id

Step	Hyp	Ref	Expression
1		cid 4763	. 2 class _I
2		vx	. . . 4 setvar x
3		vy	. . . 4 setvar y
4	2, 3	weq 1643	. . 3 wff x = y
5	4, 2, 3	copab 4622	. 2 class {<.x, y>. | x = y}
6	1, 5	wceq 1642	1 wff _I = {<.x, y>. | x = y}

This definition is referenced by:  dfid3  4768  ideqg  4868  ideqg2  4869  cnvi  5032