3. What is the goal of the three Acharyas? Brahman or Ishwara?
Brahman is called as Nirguna Brahman, when the Brahman is without Maya. When Brahman is associated with Maya it is called as Saguna Brahman or Ishwara. Maya is called as Guna (or power or quality). The quality always depends on the substance. The Substance is Brahman. Brahman is even beyond imagination as said in the Veda. The Maya is nothing but the simple awareness, which is the mind of Brahman. We can only say that the Nirguna Brahman exists as said in the Veda (Asteetyeva Upalabdhavyah) and nothing more is known. There are only two authorities to know the existence of Nirguna Brahman: 1. The Veda 2. Anumana Pramanam—for this world which exists, there must be some cause.
Scholars say the same (Aptavaak Anumanaabhyam Sadhyam). All the three Acharyas could go only up to Maya, which is pure awareness. This world is the modification of Maya. Therefore they could touch the root cause of this world which is Maya. But they could not touch the base of this Maya, which is the Nirguna Brahman. Since Nirguna Brahman is beyond imagination, it can be never touched. Therefore all the three Acharyas called this simple awareness (Maya) as Brahman because nobody can go beyond the Maya and touch the Nirguna Brahman. Nobody can even explain the process of generation of Maya from Nirguna Brahman.
How can one explain the production of the world from Nirguna Brahman directly? The world is only the modification of Maya. Therefore Ishwara can be the cause of the world through His power Maya. Ishwara without Maya (Nirguna Brahman) cannot be explained as the direct cause of the world. Shankara explained all this. When people misunderstood His theory, Shankara came as Ramanuja and Madhva to clarify the misunderstandings and condemn the misinterpretations of the true theory.
The word Brahman mentioned by the three Acharyaas is only Ishwara (Saguna Brahman) because Nirguna Brahman is beyond even imagination. Even in the case of Ishwara, only the power associated with Him called as Maya, which is simple awareness or His mind, could be touched as the cause of the world. The actual internal form of Ishwara (Nirguna Brahman) could never be touched. Similarly in the case of human incarnation also, the internal form is the Nirguna Brahman and cannot be touched. You can only see and worship the external form (human body) which is called as Prakriti and which is the modification of Maya.