Why should the Acarya have sought a debate with Mandanamisra, the mimamsaka? ( A mimamsaka is an adherent of Purvamimamsa. We Uttaramimamsakas are called "Vedantins". ) The Acarya it was who revivified the Vedic religion and re-established it on a firm footing. Why, then, should such a preceptor have been critical of Mimamsa which is an Upanga of the very Vedas we prompted?
Before answering this question, we must consider the goal of any sastra or system, whether it be Mimamsa or anything else. Any discipline, to repeat what I said before, must have the ultimate purpose of leading us towards Isvara. I further observed that even subjects like grammar, lexicography, prosody had such an end in view and that was the reason why they were included among the fourteen branches of Vedic learning. Now what is the concept of God like in Purvamimamsa?
We must here consider how Vedanta or Uttaramimamsa views God, for it is the system to which is the Acarya gave his whole-hearted support and which he also commented upon. After all, it is the Acarya who chiefly matters to us. And to him it is that Vyasa's Brahmasutra matters most. What does this text have to say about Isvara?
The Brahmasutra declares : "Karta sastrarthavattvat. " It means Isvara is the creator of the cosmos. Even adherents of other religions call God " Karta ". But Isvara is more than a Karta and has one more function. We do good and bad - good actions and bad actions. It is Isvara who vouchsafes us the fruits of such actions: "Phalam ata upapatteh". Isvara is the "phaladata" (giver of the fruits of our actions) of our karma. We do good and evil with our mind, speech and body. The lord is witness to all this and he dispenses the fruits of our actions. These are the two characteristics (laksanas) of Isvara according to Uttaramimamsa.
What does Purvamimamsa say about Isvara?
Both Sankhyas and mimamsakas belong to the Vedic system. But the Sankhyas believe that Isvara is not the Karta or author of the jagat (universe). "Isvara is pure knowledge, jnana, " they say. "This cosmos is insentient, made of earth and stone. What constitutes jnana cannot be the cause of insentient matter. To believe that Isvara is the author of the universe is not right. "Such is the Sankhya view. Supporters of Sankhya describe Isvara, who unattached to the universe and is pure jnana, as "Purusa". It is this Purusa that our Acarya calls the ultimate "Nirguna-Brahman" (the Brahman without attributes). However, he criticises the Sankhya concept maintaining that the Nirguna-Brahman itself becomes the Saguna-Brahman of Isvara to create the world and to engage itself in other activities.
To mimamsakas only such rites matter as are enjoined on us by the Vedas. They are silent on the question of Isvara and of who created the world. However they are emphatic on one point - that Isvara is not the one who dispenses the fruits of our actions. They don't quarrel on the point of whether or not Isvara is the Karta of the universe. They declare : "It is wrong to claim that Isvara gives us the fruits of our actions according to whether they are good or evil. He is not the one who metes out the fruits of our actions. It is the Vedic works performed by us that decide the fruits to be earned by us. "
So adherents of both Sankhya and Mimamsa, in their different ways, reject the view of the Vedas and the Brahmasutra that Isvara possesses the two laksanas mentioned earlier. The mimamsakas believe that Isvara doesn't dispense the fruits of our actions because, according to them, the Vedic works we perform give rewards on their own. We earn merit or demerit according to how the Vedas and sastras view our actions. So it is our karma that brings its rewards or retribution, as the case may be, not Isvara.
Among the religious systems that accept the Vedas, Sankhyas and Mimamsa alone hold the view that Isvara is not the creator of the world, that he does not award the fruits of our actions.
For a general background, please see here