[1.] An entity can exist in the understanding but not in reality
[2.] Existence in reality is greater than existence in the understanding alone
[3.] It is possible for an entity with all maximally great properties to exist in reality
[4.] From [3.] an entity with all maximally great properties plus existence in reality can exist in the understanding alone
[5.] The entity is greater than itself, according to [1.] and [2.]
[6.] [5.] is a contradiction
[7.] Therefore an entity with all maximally great properties exists in reality
[2.] Existence in reality is greater than existence in the understanding alone
[3.] It is possible for an entity with all maximally great properties to exist in reality
[4.] From [3.] an entity with all maximally great properties plus existence in reality can exist in the understanding alone
[5.] The entity is greater than itself, according to [1.] and [2.]
[6.] [5.] is a contradiction
[7.] Therefore an entity with all maximally great properties exists in reality