When the middle term is both positively and negatively related to the major term, the inference is called

When the middle links to the major both affirmatively and negatively, the inference is anvaya-vyatireki.

Anvaya establishes agreement in presence: where the reason is, the probandum is.

Vyatireka establishes agreement in absence: where the probandum is absent, the reason is absent.

Having both a positive and a negative concomitance defines this type.

A purely positive one is kevalanvayi and a purely negative one kevala-vyatireki.