Dr Livingstone, I presume?

Dr Livingstone, I assume?

Which of these sounds right? Does the first ring true just because we’ve heard it so often, or is there a difference between the two words?

Assume and presume both mean to take something for granted as true (among their many other definitions which are itemised below). The difference lies in the degree of certainty. A presumption is more authoritative than an assumption. To presume is to make an informed guess based on reasonable evidence, while to assume is to make a guess based on little or no evidence. H.W. Fowler’s opinion was that in using presume, the speaker believes the supposition is true and will believe it until he learns otherwise. In using assume, the speaker feels no certainty that his supposition is true or not. This would certainly apply to Stanley’s discovery of Livingstone, when presume would be correct as there were no other white men within hundreds of miles.

Other definitions of presume

• To take for granted as being true in the absence of proof to the contrary:

A basic tenet of the legal system is to presume someone is innocent until proved guilty.

• To constitute reasonable evidence for proving:

A signed confession presumes guilt.

• To venture without permission or invitation:

He presumed to invite himself to the party.

• To act overconfidently, to take liberties:

He presumed he was welcome at the party even though he didn’t have an invitation.

• To take advantage of something, to go beyond the proper limits:

Please don’t presume on their generous hospitality.

Other definitions of assume

• To take upon oneself, to assume responsibility:

Against advice, the mother decided to assume her son’s debts.

• To undertake the duties of an office:

Lyndon Johnson assumed the presidency after Kennedy’s assassination.

• To take on, to adopt:

Zeus assumed the form of a swan in order to seduce Leda.

• To take over without justification, to assume control:

The generals assumed leadership after the overthrow of the left wing government.

• To pretend, to feign:

Although she was very upset, she assumed indifference.

• To take up or receive into heaven:

The Virgin Mary is said to have been assumed directly into heaven without mortal decay.

• To suppose something for the sake of argument:

Let’s assume that another two million people are likely to come and live in Auckland and then review what the implications are.