We assume many folks might have the same thought we did upon learning today marks the birth anniversary—in 1813—of Scottish missionary and explorer David Livingstone. Livingstone, of course, is associated with Henry Morton Stanley's supposed greeting in what is now Tanzania: Dr. Livingstone, I presume? So what distinguishes presume from assume, and where do presuppose and postulate fit in? (来源：英语学习门户网站EnglishCN.com)

We begin by positing that all four of these terms imply a belief in something unproven. Henry Stanley presumed Livingstone's identity; that is, he took it for granted and felt entitled to believe it unless and until it was disproved. Stanley also made an assumption—in the sense of assume that means "accepted in accord with what evidence is available."

But we draw the line at the idea that Stanley was involved in postulation when he inquired of the man he had been seeking for years, Doctor Livingstone, I presume? That's because postulate is used for an assumption acknowledged as indemonstrable but accepted as true because it is indispensable as the basis for some thought series or procedure. Clearly, Stanley was not doing that. In our view, however, presuppose was as apt a word choice as the purported presume: to presuppose is to take for granted something as true or existent; that "taking for granted" can range from a hazy, casual, or uncritical acceptance or belief to a certainty through the requirements of logical causation.