Not a quote about rationalism, but probably relevant to Less Wrong:

Pure Death

We looked, we loved, and therewith instantly

Death became terrible to you and me.

By love we disenthralled our natural terror

From every comfortable philosopher

Or tall, grey doctor of divinity:

Death stood at last in his true rank and order.

It happened soon, so wild of heart were we,

Exchange of gifts grew to a malady:

Their worth rose always higher on each side

Till there seemed nothing but ungivable pride

That yet remained ungiven, and this degree

Called a conclusion not to be denied.

Then we at last bethought ourselves, made shift

And simultaneously this final gift

Gave: each with shaking hands unlocks

The sinister, long, brass-bound coffin-box,

Unwraps pure death, with such bewilderment

As greeted our love's first accomplishment.

--Robert Graves