The duality of true or false is all very well, but what if it is not known whether something is true or false? How do you use the Indus script to indicate a lack of information?
The answer can be found in the concept of shunya or emptiness. The symbol for shunya was originally a dot (bindhu). A dot in Indus script represents the word empty. The correct translation will depend upon the context. In instances where points of light or darkness, denoting true or false, would be expected, a dot signifies that the information is not available and translates as 'don't know'.
For image credits, please see below.
This is the Indus symbol for a domesticated animal with the addition of four dots, one at each of the cardinal points. In other words, it is not known where the animal comes from. Hence, Mahadevan's sign number 1036 is the noun stray.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-1673 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 10: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
In the one example of which I am currently aware, the Indus sign on the left was used with the verb to signal. In context, the plural noun strangers would be an appropriate translation.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-326 d: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 82: Collections in India: Suomalainen Tiedeakatemia.
Comment:
Seal M-326 has text on five sides.
Image Credits:
Indus Script Sign Number 1036: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.
Ternary Logic and Emptiness: Lynn Fawcett, 2017.