necessarius

Necessarius, necessaria, necessarium, built on necesse. It takes a dative of the person or thing for which something is needed: cibus corpori necessarius. The neuter singular works as an impersonal, necessarium est with ut and the subjunctive or with an infinitive, and the neuter plural necessaria means the necessities, the supplies.

The trap is the noun. Used of a person, necessarius is a close connection - a kinsman, an intimate, someone you are bound to by blood or obligation - and translating it "a necessary man" turns Cicero's circle of friends into a list of equipment. The adverb is necessario, "of necessity", which in a scholastic argument means logically and not merely inevitably.