The 17 pages of his musings on marriage in his own spidery handwriting offer a fascinating - and deeply moving - glimpse into the thoughts of a man torn between his intellectual discipline as a scientist and his desire for a wife.
It is the first time that the general public has been able to examine the 90,000 individual documents that form his archive, which provide a very human commentary on one of the greatest Englishmen of all time.
Wife-to-be: Emma Wedgwood (left) and meticulous thinker Charles Darwin
It's hard to imagine any 29-year-old man today completing such a careful analysis of the pros and cons of taking the plunge. But then, Shropshire-born Darwin was a scientist to his fingertips and wanted to leave nothing to chance - not even matrimony.
And so he wrote this manuscript in the late summer of 1838, barely two years after he'd completed his famous five-year voyage on the HMS Beagle to the Galapagos Islands, the west coast of South America and the Pacific islands, a trip that was to form part of the basis of his 1859 masterwork The Origin Of Species.
There was a very specific reason why. That summer, the young Darwin had glimpsed a young woman whom he thought he might just marry - his charming, cultured and intelligent cousin Emma Wedgwood, granddaughter of the renowned pottery designer and manufacturer Josiah.
She was just nine months older than he was.
Nevertheless as a scientist, and a Victorian at that, Darwin was not about to rush into any decision, and decided to write down the arguments as methodically as he had noted the species on the Galapagos islands, then discuss the whole matter with his fearsome father Robert, a society doctor and financier.
Taking a sheet of blue parchment paper he touchingly headed one column "Marry" and the other "Not Marry", and under each respectively noted the pros and cons.