case nil.cons => simp_all; apply Set.subset_union_of_subset_right (by simp);
α : Type u_1
Ax : AxiomSet α
head✝ : Axioms.Geach.Taple
tail✝ : List Axioms.Geach.Taple
tail_ih✝ : [] ⊆ tail✝ → 𝗚𝗲([]) ⊆ 𝗚𝗲(tail✝)
h : [] ⊆ head✝ :: tail✝
⊢ 𝗚𝗲([]) ⊆ 𝗚𝗲(head✝ :: tail✝)
no goals