The doctrine that Bhagwan Swaminarayan expounded has come out of His deep and vital personal experience, and is unique both as a philosophy and a theology. However it is Bhagwan Swaminarayan's true greatness that He has accepted the Vishishtadvait of Shri Ramanujacharya, the great Vaishnav teacher and theologian, as His philosophy with a few modifications.
During His tour around India, He used to ask five questions to the heads of muths and other preceptors:
1. What is jiva?
2. What is ishwar?
3. What is maya?
4. Describe Brahma
5. Describe Parabrahma
Bhagwan Swaminarayan has accepted five eternally existing metaphysical entities viz, jiva, ishwar, maya, Brahma (Akshar) and Parabrahma (Purushottam).
He desired to find out whether there was any correct understanding of the philosophical knowledge. He had a purpose, to find out the source of the spiritual light from which He could kindle the fire of spiritual regeneration. At last He came across a Vaishnav ashram in Loj, Saurashtra, where He found correct understanding of the philosophy. So He settled there and propounded His philosophy of Vishishtadvait. The Vishishtadvait of Bhagwan Swaminarayan is conspicuously based on the relationship between Akshar (Brahma), ishwars and the jivas, and finally on the relationship between Akshar (Brahma) and Purushottam (Parabrahma).

The Basic Differences between Vishishtadvait of Shri Ramanujacharya and that of Bhagwan Swaminarayan
We shall refer only to the essential points of metaphysical difference:
(1) According to Shri Ramanujacharya, matter (achit), soul (chit) and God (ishwar) are the three metaphysical real entities, whereas Bhagwan Swaminarayan has accepted five eternally existing metaphysical realities viz., jiva, ishwar, maya, Brahma (Akshar) and Parabrahma (Purushottam).
(2) According to Bhagwan Swaminarayan, the jivas, ishwars and maya constitute the sharir (body) of Brahma (Akshar), and Akshar is their shariri (sustainer). And since Akshar (Brahma) is:
(i) pervaded by God (Parabrahma),
(ii) absolutely dependent for his functioning upon God (Parabrahma), and
(iii) incapable of doing anything except through the shakti (power) of God (Parabrahma),
Akshar is held to be the sharir of Purushottam (Parabrahma), and Purushottam is Akshar's shariri. However, God (Parabrahma) according to Bhagwan Swaminarayan does not directly support the finite realities for any purpose of His own. He rather enables these realities to realise their own purposes.
No doubt, Shri Ramanujacharya also accepts the sharir-shariri relation between other lesser realities and God respectively, but his definition of sharir implies that it is completely controlled and supported by shariri for His own ends.
(3) According to Shri Ramanujacharya the motive which prompts God to create the world comprising of all kinds of sentient and non-sentient beings dependent on His volition, is nothing but divine sport, play.
According to Bhagwan Swaminarayan the creation by God is for the benefit of the jivas only. The universe is by no means a playground for God, but a platform from which the jivas can endeavour to get their release. Thus it indicated the purely redemptive activities of God in the process of creation, sustenance and dissolution.
(4) Shri Ramanujacharya has propounded only videha mukti (liberation after leaving the corporeal body). But Bhagwan Swaminarayan has propounded the jivan mukti concept (i.e. liberation within this life). The holding of a physical body is not incompatible with the release of the soul from maya or the shackles of karma.

Some Salient Features of the Philosophy of Bhagwan Swaminarayan
1. Ishwar
Ishwars are many but the whole category is described as ishwar. Ishwars are cosmic gods. Their bodies are composed of panch mahabhuts (five great elements). Jiva is alpagna, i.e. little-knowing, and ishwar is sarvagna, i. e. omniscient. Ishwar has three bodies, viz., virat, sutratma and avyakruta and is involved in the creation, sustenance and destruction of the universe. Ishwar is also bound by maya, since he is attached to the activities of cosmic creation.
2. Akshar (Brahma)
Akshar has been held as the sustainer and all-supporter of the millions of macrocosms. Akshar owes his greatness to Purushottam (Parabrahma), as Akshar is controlled by Parabrahma as its shariri. Akshar as the Atma of all the atmas (the Soul of all the souls), possesses unitive consciousness with Parabrahma, yet is conscious of his dependence upon Purushottam (Parabrahma).
Bhagwan Swaminarayan upheld Akshar (Brahma) and Purushottam (Parabrahma) as separate entities, and defined their relationship as: Akshar (Brahma) is related to Purushottam (Parabrahma) as drashya-drashta, sharir-shariri and niyamya-niyamak. Parabrahma pervades, controls and subdues Akshar.
Akshar (Brahma) is the divine abode of God (Parabrahma), serving God in two ways. As the divine abode, Akshar supports Purushottam and the infinite number of released souls; and as His choicest devotee, Akshar serves Purushottam (God) in revealing His infinite greatness and glory. Akshar is beyond maya or prakruti and is savayav i.e. having a divine body.
One desiring ultimate redemption should identify himself with Brahma (Akshar) and worship Parabrahma (Purushottam) as his God, upholding the ideal of swami-sevak bhav (master-servitor relation).

Concept of Mukti (Ultimate Redemption)
The core of the doctrine of this Sampraday is the belief in the living personal God, who is known as Purushottam. According to Bhagwan Swaminarayan Parabrahma (God) manifests Himself, out of His infinite mercy, along with other released souls, to redeem His beloved devotees who have faith in Him and who have taken refuge and who have surrendered totally at His lotus feet. He brings grace and salvation unto them.
God always manifests Himself on the earth either in His own divine form or when He reverts to His divine abode, He manifests in His full splendour through a brahmanised (God-realised) Sadhu. The meditational worship of Brahma or a brahmanised Guru through whom God is worshipped and the observance of five fundamental tenets which forbid indulgence in passion, covetousness, taste, attachment and egoism, are the cardinal requirements for a total deliverance as enunciated by Bhagwan Swaminarayan.
Thus Aksharbrahma plays an essential role in the scheme of redemption of jivas by removing the ignorance of maya attached to them. When the empirical self (jiva) knows Akshar through wisdom, service and devotion, shedding the ego, the jivas attain identification with Akshar. One desiring liberation should so identify himself with Akshar (Brahma). Then just as ice, which is frozen water, resumes its liquid form through heat, so through the spiritual alchemy of Akshar, the jivas attain the state of atmavalokan, of gnan or full knowledge. He becomes brahmanised, enjoys the grace of Parabrahma (Purushottam) and attains ultimate redemption. Thus ultimate redemption, or brahmic consciousness, is not attained by sadhanas but by grace only. Hence, one desiring ultimate redemption should identify himself with Brahma (Akshar) and worship Parabrahma as his God, upholding the ideal of swami-sevak bhav (master-servitor relation).
In the state of liberation, the released soul does not remain still or dormant but has spiritual activism, with which he sings the praises of God in His full splendour. The awareness of the transcendence of God is always before the released souls, which in turn keeps them always subservient to God.
It is therefore believed in the Fellowship that Bhagwan Swaminarayan is Himself Parabrahma, and that the final mukti is attained by only those who dedicate themselves totally at His lotus feet (i.e. through prapatti).

Vishishtabrahmadvaitatvam
In the state of final emancipation (atyantik kalyan), every released soul enjoys God's bliss. It is a state of identification with God, but not of assimilation, rather like the relationship between body and soul. In this state of release, which is also a state of ultimate knowledge, the differences of jiva, ishwar and maya which were real in the empirical state are eliminated. In the state of total bliss, Brahma remains absolutely engulfed, losing all consciousness of separateness from Parabrahma. In the final state, Parabrahma alone remains, with the qualified adjunct of Akshar (Brahma). Thus Shri Krishnavallabhacharya, an eminent scholar on the philosophy of Bhagwan Swaminarayan, terms this as 'Vishishtadvaita api vishishtabrahmadvaitatvam,' which means that Purushottam (Parabrahma; God), the one and unparalleled (advait), is qualified only by Akshar (Brahma) - an unexcelled doctrine, not only in the school of Vishishtadvait but in the whole world of Vedantic Philosophy.

Conclusion
Bhagwan Swaminarayan emphasised the necessity of reconciling reason and intuition in order to attain knowledge of the Ultimate Reality - God. He evolved a unique philosophy of universal appeal, which satisfied the needs of worship and devotion and could also meet the claims of reason.
The succession of brahmanised sadhus and teachers right upto the present day is according to Bhagwan Swaminarayan's divine promise to remain manifest constantly on the earth for the salvation of devotees and spiritual aspirants. His divine message is perennial as is His divine hierarchy through brahmanised (God-realised) souls whose life and teachings are in absolute consonance with the spiritual, ethical and theological precepts of Bhagwan Swaminarayan.
Bhagwan Swaminarayan was succeeded by Shri Gunatitanand Swami, who was the very incarnation of Akshar (Brahma). He inspired his foremost disciple Shri Pragji Bhakta who was his spiritual successor, who in turn was succeeded by Swamishri Yagnapurushdasji. Then his spiritual successor Swamishri Gnanjivandasji brought divine knowledge to many different parts of the world, and the torch of brahmic consciousness is today borne by Swamishri Narayanswarupdasji, popularly called Pramukh Swami Maharaj.