A man whose word will not inform you at all what he means or will do, is not a man you can bargain with.
 Thomas Carlyle, On Heroes, Hero-Worship, and The Heroic in History (1841). copy citation

Context

“Forsaken there of all but the name of Kingship, he still, finding himself treated with outward respect as a King, fancied that he might play off party against party, and smuggle himself into his old power by deceiving both. Alas, they both discovered that he was deceiving them. A man whose word will not inform you at all what he means or will do, is not a man you can bargain with. You must get out of that man's way, or put him out of yours! The Presbyterians, in their despair, were still for believing Charles, though found false, unbelievable again and again. Not so Cromwell:” source