Why प्रादयः (1-4-58) and उपसर्गाः क्रियायोगे (1-4-59) are द्वे सूत्रे
I do not know how and why, but just came to mind प्रोक्तमन्वभवत् (प्रोक्तम् अनु+अभवत्) This phrase can be paraphrased in two ways प्रोक्तम् अनु अभवत् = It happened as was said. This is like a prediction of an astrologer coming true. प्रोक्तम् अन्वभवत् = He experienced what was said. Note, the two English phrases "It happened" and "He experienced" have different subject-words 'It' and 'He'. In "प्रोक्तम् अनु अभवत् = It happened as was said" the word अनु is related to प्रोक्तम्. In प्रोक्तम् अन्वभवत् the word अनु is integral with अभवत्, i.e. the word अनु has क्रियायोग:. A word like अनु is उपसर्ग: when there is क्रियायोग:. That is the precise purpose why प्रादयः (1-4-58) and उपसर्गाः क्रियायोगे (1-4-59) are द्वे सूत्रे. When they are more related with another word as in प्रोक्तम् अनु, then they are प्रादयः. It is said that श्रीरामायणम् प्रोक्तम् अनु अभवत् i.e. श्रीरामायणम् happened as was scripted (by वाल्मीकि). Alternatively श...