That each, who seems a separate whole, Should move his rounds, and fusing all The skirts of self again, should fall Remerging in the general Soul,
Is faith as vague as all unsweet: Eternal form shall still divide The eternal soul from all beside; And I shall know him when we meet:
And we shall sit at endless feast, Enjoying each the other's good: What vaster dream can hit the mood Of Love on earth? He seeks at least
Upon the last and sharpest height, Before the spirits fade away, Some landing-place, to clasp and say, "Farewell! We lose ourselves in light."
The idea that each person will recognize himself as a separate being while alive, but then merge back into a general Soul that sounds suspiciously like the Borg Collective is a doctrine ("faith") that doesn't sound too good to Tennyson.
He professes that there's something about the form or individual soul that remains separate from the eternal one, and that he'll be able to recognize Arthur in the afterlife. The two will enjoy each other's company forever—what more can anyone hope?
At the very least, if there is this Borg-like One-Soul at the end of things, people ("he" is used universally here) want a moment to say good-bye before they are assimilated.
There's that "light" again. Even though Tennyson is faced with the proposition of an impersonal One-Soul in Heaven, at least it's something positive—suggested by light instead of darkness here.