2 4 A Key Difference Between SOI and DOI

SOI and DOI have one prominent feature in common: in case of both SOI and DOI, two (or more) rules are simultaneously applicable at a certain step of the derivation. However, it is important to shed light on a key difference between SOI and DOI. This difference between SOI and DOI pertains to whether or not they involve competition between two operands.

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Type 1: ( R1A R2A →) A + B

Type 2: (RA→) A + (RB→) B

In case of DOI, we see that the two simultaneously applicable rules RA and RB compete for the sole position of the rule that applies at that step. But the two operands A and B too compete for the sole position of the operand that undergoes an operation at that step.

In case of SOI, the two simultaneously applicable rules R1A and R2A compete for the sole position of the rule that applies at that step. However, since both are applicable to the same operand A, we do not observe any competition between operands.

Because Pāṇini has not given any instructions about SOI, but has taught the metarule 1.4.2 for dealing with DOI, we can say that Pāṇini has given explicit instructions about how we must deal with competition between operands (which we see in DOI but not in SOI), but not about how we must deal with competition between rules (which we see in both DOI and SOI).

Thus, we must understand vipratiṣedha in 1.4.2 not as mutual opposition between rules but rather as mutual opposition between operands.