“Today we can no longer understand the stubborn reisitance to the new numerals during the early Middle Ages; to us they seem so much easier to work with than the cumbersome Roman numerals. . . . [T]he counting board served medieval Europe as a perhaps slow but essentially equivalent and above all highly visual means of computation. Computations with the new numberals, in contrast, were certainly not as easy to visualize. But most of important of all they embodied an intellectual obstacle that was scarcely overcome during the first few centuries of their presence in the west: the zero!

What kind of crazy symbol is this, which means nothing at all? Is it a digit, or isn’t it? 1, 2, 3, 4, 5, 6, 7, 8 and 9 all stand for numbers one can understand and grasp — but 0? If it is nothing, then it should be nothing. But sometimes it is nothing, and then at other times it is something: 3 + 0 = 3 and 3 – 0 = 3, so here the zero is nothing, it is not expressed, and when it is placed in front of a number it does not change it: 03 = 3, so the zero is still nothing, nulla figura! But write the zero after a number and it suddenly multiplies the number by ten; 30 = 3 x 10. So now it is something — something incomprehensible but powerful, if a few ‘nothings’ can raise a small number to an immeasurably vast magnitude. Who could understand such a thing?”

—Karl Menninger, Number Words and Number Symbols; A Cultural History of Numbers, 1969.