Universal 279: zero person marker (indicative mood) ⇒ 1Sg v 3Sg
Original
If a zero expression occurs in the form of a certain person in the indicative mood, then, included in the meanings thus expressed (i.e. by a zero mark) we find the meaning of the 3rd person or that of the 1st person.
Standardized
IF any person has zero expression in the indicative mood, THEN it will be 3rd person singular or 1st person singular.
Put implicationally: If any other person.number has zero expression, then 3SG or 1SG will also have zero expression.