Whenever a Supreme Court confirmation hearing approaches, this quote from Abraham Lincoln tends to come up (e.g., here):
We cannot ask a man what he will do, and if we should, and he should answer us, we should despise him for it.
I thought I’d pass along, though, the full context. The quote, as best I can tell, comes from George S. Boutwell’s Reminiscences of 60 Years of Public Affairs, vol. 2, p. 29 (1902), who reports that Lincoln had said (apropos the nomination of Salmon P. Chase to be Chief Justice):
[W]e wish for a Chief Justice who will sustain what has been done in regard to emancipation and the legal tenders. We cannot ask a man what he will do, and if we should, and he should answer us, we should despise him for it. Therefore we must take a man whose opinions are known.
A somewhat different meaning, it seems to me.
And one more twist: While Lincoln rightly estimated Chase’s views on emancipation, Chase ultimately voted against Lincoln’s expectations — contrary to his supposedly “known” “opinions” — to provide the swing vote striking down the legal tender legislation that Chase himself had helped create. (That decision was itself reversed within a year using the votes of two newly appointed Justices. Some say those two Justices were themselves appointed because they were seen as likely to uphold the legal tender law; and they, unlike Chase, complied with the expectations.)