'Suffer the little children to come unto me, and forbid them not: for of such is the kingdom of God.' Mark 10: 14
What is possibly the most remarkable trait about Jesus Christ's position in Blake's cosmology is that he is quite likely the only dominant character whose function and purpose remains static throughout the poems, a very telling observation considering the protean nature of Blake's rather fluid dramatis personae, where any particular spirit or person might represent one thing in the first instance, and then something entirely different in the second. In sharp contrast to these vacillations in symbolic reference, Jesus Christ does not change in an substantive aspect.
The primary purpose of the Christ is, of course, soteriological; he is the true Messiah who arose from the passivity of death to ascend into spiritual activity, viz. the kingdom of Heaven. This perennial 'hero image' achieves its effect of universal salvation through a vicarious relationship between the resurrection of Christ and the poetic, individual understanding of the iconic symbol that the apotheosis presents; Blake is in full comprehension of this process when he assigns Jesus the herculean role of lifting the newly aware individual into spiritual awakening, as in the end of Jerusalem, and the supplementary role of the Judge, the supreme arbiter of the Just and the Wicked, as in the 'Designs of the Last Judgment'. In either role, Jesus adopts a position of governance that encompasses all humanity either symbolically, through the metaphor as Jesus the universal redeemer, or quasi-literally, through the judgment of all mankind.
This unique task leads us to the deliberation over Christ's greatest function in Blake's vast symbology: the ultimate assimilator (or 'subsumer') of man as an individual. We briefly mentioned above the problem of retaining particularity whilst ascending into universality without offering the clear and specific solution; Blake says that, 'As a mas is So he Sees', so how does this man, who has a different perspective than everyone else, gain entrance into the universal humanity, the 'Four-fold Man' which is more or less wholly unconditioned? The 'more or less' actually exonerates Blake of this issue, since the general form of humanity really is ascribed with a precise and definite structure that directly corresponds with the body parts of the human figure. Thus, every individual has his own unique role (i.e., part of the hand, foot, mind, etc.) to fulfill in order to become an integral part of the single body. This 'inner destiny' is achieved through the Christian relationship with the Godhead, Christ Himself, who subsumes the particular into the universal via the particular's peculiar mode of higher hermeneutics, or the realization of his spiritual and natural constitution according to the principial dharma (crudely translated as 'law') underlying all phenomenal reality. In this way (which is presently explained through a much heavier means than the lucid poetry itself), where the relative is reconciled with the absolute through the identification of his core being with that of the singular 'Four-fold Man', Blake has truly created his own comprehensive 'system' that is, once again, paralleled to Platonic thinking in both the West and the East.
'As all men are alike (tho' infinitely various) So all Religions & all similars have one source.' ~ 'There is No Natural Religion'
Finally, it is no coincidence that the character Jesus Christ enters the act near the end, or that his role in 'Vision of the Last Judgment' is central; the significance lies in the fact that the individual never really beholds Christ until the last vestige of worldly existence is stripped away, and then the shining glory of his almighty redeemer is all that he sees. This strongly relates to the white of Apocalypse, where everything somehow conditioned is eradicated in the pearly sheen of spiritual catharsis. Until this final point where we may behold the awesome beauty of Heaven itself, we can only understand its spiritual nature through symbolic reality, and the only way to understand the ladder that ascends to Heaven is through the symbolic reality of Christ Himself.
Blessed and holy is he that hath part in the first resurrection: over these the second death hath no power; but they shall be priests of God and of Christ, and shall reign with Him a thousand years. Revelation 20:6