In the dawning of the age of science, leading thinkers advocated a strongly empirical way to understand the world: through observation, what we now call science. The widely held belief in this period, known as the Enlightenment, was that empiricism would reveal knowledge of the nature of Nature that would enable humans to engineer a better more perfect society--a Utopia. This society would rectify physical needs as well social inequities.
At the beginning of this era, Newton's and Galileo's physics had powerfully showed that if based on observation rather than received doctrine or faith, the world followed natural law. Natural laws unchangingly governed the universe: they dictated how the stars did, do, and would forever go 'cycling on according to the fixed law of gravity'. That phrase is in Darwin's last paragraph in the Origin of Species (1859), but Darwin had anything but a static world in mind: instead, he was the century's icon of unremitting, mechanical change.
Darwin's insights reflected, were influenced, enabled, and inspired by the advances in geology showing that, while not static, geological processes were very slow and sometimes cyclical. As a famous founding article in geology by Hutton (1788) ended: 'no vestige of a beginning, no prospect of an end.'
But Darwin showed that life on earth was changing in a gradual, but very different way: it was evolving, and from a beginning! Darwin refined and reflected thinking by many others, who were suggesting general ideas about evolution, including about the evolution of life. Many were relating scientific ideas about laws of change to society itself: Herbert Spencer, Karl Marx, and others were suggesting that society was as much subject to laws of Nature as the earth and life were. This thinking about society, (and to some extent Darwin's thinking about life, and that of many of his contemporary evolutionists), included a strong sense of progress. In ways resembling Enlightenment Utopian thinking, they saw society as evolving from primitive states, to civilization, and on towards some idyllic end: life had evolved the noble brow of humans, and society would evolve to be more equitable.
These were all about material laws, and one might think they would drive definitive nails into the coffin of changeless, religious thinking, based as it was on received word rather than observed fact. How on earth (so to speak) could anyone speak of 'Heaven'? In fact, however, at the time many writers suggested that the progress in earthly evolution was leading to a perfected end-state, often envisioned as being 'with God' and that this march of progress was in fact ordained by God.
Of British intellectuals, Tennyson was among the most interested in, and aware of, contemporary science. In Memoriam was published in 1850, some years before Origin. But evolution in life and geology were in the air, and others had been writing about evolution (in particular a book by Robert Chambers called Vestiges of Creation, 1844), and in the kinds of progressive terms we mentioned above. The earth and its life were working out God's plan so that its perfecting creature--humans--would eventually be worthy of, and end up with, God. The progress in society and in the more complex organisms on earth than had been here before, suggested that change was heading to a goal that the evidence made obvious.
This view--or hope--provided the only solace of Tennyson's mourning, and he could look to the science we've just mentioned to support that hope. The earth was mechanical, cruel, relentlessly dishing out sorrow. All here was temporary, all would disappear as streams 'Draw down aeonian hills/The dust of continents to be,' and those who once lived 'seal'd within the iron hills.' As for species 'a thousand types are gone....all shall go.' into the bowels of history! If there was no way to really recover from the death of close friends, the relentless earth meant there was no way to escape from it, either. Tennyson would never again shake Hallam's hand or hear his voice, at least not in this world. But he consoled himself by writing that Hallam was a creature ahead of his time, 'a noble type, Appearing ere the times were ripe', and his disappearance may have been because he was too good for his time. But if Hallam had been taken from him for the time being, Tennyson yearned and dreamt, hopefully, for the day they would be reunited in a perfected world. There will come a 'crowning race....No longer half-akin to brute....to which the whole creation moves.'
The Rapture redux, in the raiment of science
For a while, especially before Darwin, one could do as Tennyson did, and absorb the factual realities of earthly change into the teachings of some aspects of religion. But as science progressed, and the implications of biological evolution were realized, it became less and less possible to see either real progress in how life worked, or to find any evidence of a march to a specifiable, much less seeable, end on the evolutionary horizon. Eventually, the earth would burn up or burn out, and return to the unrelenting cold womb of space, and life would go with it.
How could someone who had absorbed the idea of change--even progressive change--have ever got the idea that there would be a end-point? Well, if the 2nd law of thermodynamics says the universe is moving towards maximum disorder (called 'entropy'), or randomness of matter and energy, then why can't there be some biological or societal end-point? The comparable point to entropy might be when there was no social inequality, or when the mind had reached the maximum perfection (that was called 'God'). It's a stretch, because in a sense it implies there's a maximum IQ for God's perfecting creatures to reach (maybe that's God's IQ?). In any case, define it how you want, one can imagine, or invent, such states. Still, there was no evidence for them--in life, or in society.
Darwin may have grudgingly agreed that there might be a God who started it all, but the clockwork mechanism of evolution provided no goal or endpoint for life, nor so far as we know did Darwin ever make any such suggestion. And as science has worked it out over the subsequent 150 years, our understanding of life as the product of evolution has largely closed the coffin lid on such goal-headed views of life. If one wants to believe in a theistic religion, an Omega state, an after-life, or a benevolent deity, we know that one must seek it in some non-material rationale: the scientific study of the material earth simply doesn't provide any empirical support for such views. Except perhaps that 'intelligence' will lead to rapid human-induced extinction of our own and all other life....
Religion does, however, calm and solace people from seeing the world in its stark, remorseless reality. In Memoriam expresses the value of such a view. Tennyson's grief was so deep that he needed at least that hope to hold onto, even if tentatively and with doubt--'Believing where we cannot prove'. Even today it is a poem to be read, and as discussed in In Our Time, one that has given solace to many persons weeping in the long, dark night for a lost loved-one:
Tears of the widower, when he sees
A late-lost form that sleep reveals,
And moves his doubtful arms, and feels
Her place is empty, fall like these.
Perhaps the often-strident and prideful Darwinian atheists should take some pause. They too, and you, and we, will someday experience Tennyson's grief. Illusion? Maybe. But there is more to life than science.
A warmth within the breast would melt
The freezing reason's older part,
And like a man in wrath the heart
Stood up and answer'd "I have felt."
Tennyson's is a view not to be frivolously dishonored, even if the evolution of the science of evolution has unremittingly evolved away from any such notions of progress towards an idyllic endpoint. Or, even, from wishful thinking.