x:A. (x,y:A. Dec(x = y)) 
(L:A List. Dec((x 
L)))x:T. (x nil) 
Falsel:T List, a,x:T. (x [a / l]) x = a 
(x l)| Rank | Theorem | Name |
| 2 | x:A. (x,y:A. Dec(x = y)) (L:A List. Dec((x L))) | [decidable__l_member] |
| cites the following: | ||
| 0 | x:T. (x nil) False | [nil_member] |
| 1 | l:T List, a,x:T. (x [a / l]) x = a (x l) | [cons_member] |