All assertions infinitely regress to a series of common assertions, thus necessitate all assertions having an inherent middle term. Each middle term in itself is a regress thus necessitating all middle terms as a series of underlying assertions which multiple phenomena have in common.
(Toaster --> Metal --> Copper --> Electrons)
(Cow ---> Bone ---> Minerals ---> Copper ---> Electrons)
___________Copper --> Electrons___________
((...) ---> Toaster --> Metal ---> (....))
((....) ---> Cow ---> Bone ---> Minerals ---> (...))