The Religious Philosophy of Sankaradeva
In Sankaradeva's view, bhakti to Krishna is the realisation of the Nirguna (formless, non-dual) Parama Brahma through the gunas of Lord Krishna. His concept of Godhead, which forms the bed-rock of his religious philosophy, is that of One who is ever living and loving and the force with which the world is connected with God is both centripetal and centrifugal.
It is monothesim to be sure, and it is so even in a severe sense. Mahapurusism of Sankaradeva had no reason to have any mutation, still less any affiliation, with Absolute Monism of Sankarāchārya or with Qualified Monism of Rāmānujāchārya, not to speak of the faiths of their followers. If there could be any question of mutation or affiliation still, it could have been with the Gitā and the Bhāgavata direct which Sankaradeva read and interpreted in his own way, at once original and new.
Rejection of Prakriti-Purusism
The term Mahapurusiyā (Mahapurusa meaning God), applied to the religion of Sankaradeva, is at once a challenge to Prakrti-Purusism of the Samkhyā system of Hindu philosophy and immediately stamps the originality of the philosophy of the religion founded by Sankaradeva. It is both the starting point and the point of departure.
The epithet Mahapurusa cannot be compared with the common epithets like Mahaprabhu or Mahatma that are applied to men. Even the term purusa is almost invariably used in the vast Assamese Vaisnavite literature in a restricted sense to jiva (Life) and is seldom applied to men in the ordinary sense. One need not strain one's imagination for any visible proof in this regard, and we find a direct refutation of Samkhyā in so many verses of the holy Nām Ghosā by Madhavadeva, the great disciple and successor of Sankaradeva:
Prakrti Purusa / duito kari para / duihano nija kāran:
Param Iswar / nāmak dhariā / āchā tāte Nārāyan. 
Apart both from Prakrti (Matter) and Purusa (Mind), (but) primal cause of both: whence Nārāyana assumes the name of the Great Lord.
Prakrti Purusa duiro / niyantā Mādhava:
Samastare ātmā Hari / param bāndhava. 
Mādhava (God) is the Ordainer of both Prakrti (Matter) and Purusa (Mind). Hari (God) is the (supreme) soul and great Benefactor of all.
Nārāyana Greater than even Brahma
According to the Vedanta philosophy the highest cosmos is Brahma (Ego), and there is none beyond: Etat param Brahma veda, natah param astiti (Prasn Upanisad, VI, 7). But Sankaradeva pushes boldly beyond:
Ksara pade ito / dehak bolay / aksar sabade Brahma :
Duito kari Hari / uttama nimitte / prakhyāt Purusottama. 
Ksara refers to this body; aksara to Brahma; Hari (God) being superior to both is well known as Purusa Uttama (Supreme Soul).
Purusa Uttama / Parama Purusa / Parama ānanda Svāmi:
Tayu pāda-padma / makaranda āse / sarana pasilo āmi. 
Thou the best Purusa, the Supreme Purusa and Master of Supreme Joy. I seek refuge in thee for the nectarine juice of thy lotus feet.
Thus we find that Sankaradeva not only brings in the best Purusa or Supreme Purusa in brighter relief against the bare Purusa of the Samkhyā philosophy, but superiority is claimed for the best Purusa or Supreme Purusa to Brahma (Ego) Itself, which is reduced to something like the Aristotelian God, Primum mobile immotum (Prime mover unmoved), who is a 'do-nothing king' that reigns but does not rule.
Sankaradeva begins his master-piece, the holy Kirttana:
Prathame pranāmo Brahma rupi Sanātana:
Sarva avatārara kārana Nārāyana.
First of all I bow to the Eternal Nārāyana who in the nature of Brahma (Ego) is the cause of all incarnations.
As we may see, this makes Brahma an intermediary, and not as 'Etat param Brahma veda, natah para astiti' (Taittiriya Up. II, 8; also Prasna Up. VI, 7) - “Then there is Brahma (Ego), and nothing beyond it.” Thus the originality of Sankaradeva's philosophy must strike us presently.
Who, Sankaradeva asks, can ascribe 'dvaita' or duality to God, when, on transcending the māyā or nescience, it becomes clear that the same Niranjana, or the Supreme Divinity, exists in every item of His creation? The apparent difference, he asserts, is only in nām (name) and rupa (form), as between gold and the various ornaments made out of it.
Then we come to the prayer, highly significant, in the Kirttana:
Namo namo Mādhava vidhira vidhi-dātā:
Tumi jagatar gati mati pitā mātā.
Tumi paramātmā jagatar Isa eka:
Eko vastu nāhike tomāta byātireka. 
Tumi kāryya kārana samasta carācar:
Suvarne-kundale yen nāhike antar.
Tumi pasu paksi surāsur taru trina:
Ajnānat mudhajane dekhe bhinna bhinna 
Twice do I bow to Thee, O God, the Giver of Law to the Ordainer (Brahmā) himself. Thou art the Deliverance, the Intellect, the Father, the Mother (all in one) of the world. There is nothing else than Thee. Thou art the Effect, the Cause, the whole Universe, as there is no difference between gold and gold-earings. Thou art all beasts and birds, gods and demons, trees and creepers. It is for sheer ignorance that dullards see them different.
Life (jiva) and Great Life (Paramātmā)
According to Sankaradeva, jivas (Life) are not entirely exclusive nor inclusive of God, like sparks of fire. They neither are nor were born; but they are contained in bodies as fire in wood. Again like fire which is yet different from the wood, is Life (jiva) different from the body which alone has the so called birth and death. Then what happens to life when the body is no more? The same thing that occurs to ether confined in a pot when the pot breaks. As the ether suffers no loss, so does life. As a lamp means the contact of fire with wick and oil, and its extinction only means the ceasing of such contacts, so death means only the cessation of contact of life with the body. Also, an extinction of the lamp cannot mean annihilation of fire which is ever present as light (or heat), so death does not mean destruction of life, but simply means that life in a body has merged in universal life which is ever present. So life (jivātmā) or the Great Life (Paramātmā) is in the body, but is not of the body. (Dvādas, vs. 204-210).
The concept of Māyā
Iswara is the controller of māyā through His power of consciousness (vidya saktya mayaniyanta) and jiva is ever mortified under the pressure of māyā. Jiva can be released only when it attains knowledge through the love of God (bhakti). For this Sankaradeva has chalked out a clear path and we have only to follow.
The Mystery of the Mind
Sankaradeva's Anādi Pātan gives an account of Mahapurusiyā cosmogony. It tells us how in the arc of descent life has come down from Brahma through Prakriti with the enveloping medium of this body and the physical world, and how Mind came to be born out of Māyā which alone is responsible for this conception of the so-called universe. Sankaradeva puts it excellently:
Hridyat thāki kare bhāl manda kām:
Eke Man cāri rup sunā tār nām...
Nānā karma karibāk kare ālocan:
Eko kārye sthir nohe tāk bole Man:
Samkalpa vikalpa dharma kare ālocan:
Buddhi nām buli tāk jānibā laksan.
Samasta karmak Mai karo buli māne:
Ahamkār buli tāk janibā āpone.
Nānā sad karmak karay nitya nitya:
Niscay jānibā Rājā tār nām citta...
Manar kalpana mane samasta samsār:
Jāgan svapan nidrā tini britti tār.
Āche Man samasta prānir sarirat:
Iswarar pratibimba lāgiche manat.
Tāke buli jiva Man-ere bhinna nui:
Ek pinda bhaila yene lohā agni dui.
Mane duhkha pāile Jive bole mai pāo:
Mane yaika yāve Jive bole mai yāo.
Mane yiba kare Jive bole mai karo:
Manar marane Jive bole mai maro.
Yena surya bimba lare jalar lagat:
Jal sthit bhaile bimba thāke purvavat.
Manar karmak Jive mor buli māne:
Karma pāse bandi Jive ehise nidāne.
Ātmār prasange Man howe acetan:
Manatese āche ito caidhyaya bhuvan.
Mane pāp mane punya manese narak:
Manese kariche bhin āpon parak.
Yatek indriyagan Manar adhin:
Manarese ājna pāli thāke rātri-din.
Mane opajay jānā Manese maran:
Manusyar Mane Moksa-bandhar kāran.
Yata dekhā deva-dharma Manar pravandha:
Tāve bandi thāke jiva, nerāi karma-bandha
(Mind) resides in the heart and does all good and evil deeds. Mind is one, its forms are four: hear their names...It is Mind that proposes to do so many things, but is not settled in any of them. That is Intellect which plans any making or unmaking. That is Pride which considers itself as the author of all things. That is Heart which does all good deeds from day to day... This world as a whole is the creation of the mind. Waking, dreaming and sleeping are the three faculties of the mind. Mind is there in the body of every being. The Mind catches a reflection of God. Life is that which is inseparable from the Mind, like a lump of iron which becomes one with fire. Whenever the mind is afflicted, 'So am I' says Life. Whenever the mind dies, 'So die I' says Life. It is like the reflection of the sun that moves or remains as does the water. Life is ensnared by the consequences of its own actions of this or the previous birth only because the mind thinks them to be its own doing. Mind is inanimate in reference to the soul. The fourteen universes are there only in the mind. Mind makes vice, mind makes merit, mind makes the hell. It is mind that makes people near and distant. All the organs of sense are subservient to the mind. They obey the commands of the mind day and night. Mind makes one born, mind makes one dead. Man's salvation or bondage is due to the mind. All worship of minor gods or goddesses is effort of the mind. It is why life is enslaved and cannot free itself from the bondage of consequences of acts already done.