Presume and Assume: is there a difference?
Presume and Assume, there is a subtle difference.
When the celebrated Victorian explorer and missionary Dr David Livingstone went ‘missing’ in the wilds of Africa for over six years the journalist-cum-adventurer Sir Henry Morton Stanley set out to find him. In November 1871 he eventually found Livingstone on the shores of Lake Tanganyika and legend has it that Stanley greeted him with the words “Doctor Livingstone, I presume.”
Now why did Stanley say ‘presume’ and not ‘assume’? Is there a difference? The short answer is yes there is – a subtle one.
In common usage both mean to suppose or to take something as a given, and may be used interchangeably. The difference is merely one of degree. Assume is somewhat weaker or less authoritative in meaning than presume. When a speaker is unsure of his facts he makes an assumption but when he is reasonably sure of them he makes a presumption.
So Stanley was technically quite correct. Given the circumstances, it was highly unlikely that the man beside the waters of Lake Tanganyika was anyone other than Dr Livingstone, so saying presume and not assume was correct.