Abraham Lincoln in 1856, according to Isaac N. Arnold, on p. 28 of The layman's faith: "If a man die, shall he live again?": a paper read before the Philosophical Society of Chicago, Saturday, December 16th, 1882. Arnold was channeling Mrs. Norman P. Judd, who, however, wrote only (without ever pretending to quote Lincoln),
"[Lincoln] speculated on the possibilities of knowledge which an increased power of the lens would give in the years to come; and then the wonderful discoveries of late centuries as proving that beings endowed with such capabilities as man must be immortal, and created for some high and noble end by him who had spoken those numberless worlds into existence; and made man a little lower than the angels that he might comprehend the glories and wonders of his creation."
Mrs. Norman B. Judd, "An evening with Mr. Lincoln," in Osborn Hamiline Oldroyd, ed., The Lincoln memorial: album-immortelles. Original life pictures, with autographs, from the hands and hearts of eminent Americans and Europeans, contemporaries of the great martyr to liberty, Abraham Lincoln. Together with extracts from his speeches, letters, and sayings. With an introd. by Matthew Simpson, and a sketch of the patriot's life by Isaac N. Arnold (Boston: D. L. Guernsey, 1882), 522 (520-524), where there is much more, though no occurrence of infinit* specifically. According to Don E. and Virginia Fehrenbacher, "Mrs. Judd's vagueness about the date and circumstances casts some doubt upon the reliability of this interesting [specifically Mrs. Judd's] recollection" (Recollected words of Abraham Lincoln, ed. Don E. and Virginia Fehrenbacher (Stanford, CA: Stanford University Press, 1996), 271). Recollected words of Abraham Lincoln, by the way, is a very handy work of reference that places the "recollected words" under the names of those who recollected them, arranged alphabetically, and rates each recollected statement from A to E. This one gets a D for "A quotation about whose authenticity there is more than average doubt" (liii). The more expansive recollection of the words of Lincoln on this same occasion as set down by Arnold (above), by contrast, does not appear along with the other recollections subsumed under his name at almost the head of the alphabet on pp. 18-19.
On the other hand, Isaac N. Arnold could, I suppose, have been present himself that evening, and therefore capable of elaborating on Mrs. Judd's account on the basis of his own memory of the conversation.
Compare also this account from 1886, which quotes and actually cites "An evening with Mr. Lincoln" (above).
Militating against the authenticity of this report, however, would be testimony like this, quoted on p. 50 of the 1999 edition of Guelzo's Abraham Lincoln: redeemer president (Guelzo's source, Stevens' Reporter's Lincoln, 12, attributes it to the young Lincoln, from 1831-1837 resident in [New] Salem, IL, i.e. still nineteen years or more before 1856): Lincoln "at least once admitted that he could not believe in the personal immortality of the soul. 'So you really believe there isn't any future state?' asked Parthena Hill. 'Mrs. Hill, I'm afraid there isn't,' Lincoln replied. "It isn't a pleasant thing to think that when we die that is the last of us.'"
With thanks to my friend and colleague Dr. Ben McFarland for the diversion.
