Christopher Lane has a fascinating history of agnosticism in the New Humanist, an ode to doubt. :
Then [in the Victorian era] as now, doubt requires strength – it is not an easy or straightforward position to maintain.
The impact of such doubt grew on both sides of the Atlantic, with subscription rates for freethinking journals rising substantially and a growing number of articles appearing on the topic. … The idea that doubt was a sin and a moral failing, still widely held in the 1850s, gave way to a new and different emphasis: doubt was instead an intellectual obligation, even an ethical necessity. It represented a principled position. It was not a sign of emotional weakness or a moral failing, but exactly the reverse. …
Yet it was Thomas Huxley, Darwin’s staunchest defender (and so-called bulldog), who not only coined the adjective “agnostic” in 1869, but argued strenuously for a seemingly oxymoronic “agnostic faith”. Huxley stated his rationale and advice clearly: “In matters of the intellect, follow your reason as far as it will take you. [But] do not pretend that conclusions are certain which are not demonstrated or demonstrable.”
The whole essay is worth reading, and I look forward to getting my hands on Lane’s book The Age of Doubt, of which this essay is an excerpt.