Once the distinction is made, it becomes apparent that the application of absolute terms to describe the real-world objects is doubtful.
Absolute terms describe properties that are ideal in a Platonic sense, but that are not present in any concrete, real-world object.
When we look at a rather smooth block of stone through a powerful microscope, the observed surface appears to be rife with irregularities.
And this irregular appearance seems best explained, not by its being taken as an illusory optical phenomenon but, by our taking it to be a finer, more revealing look of a surface which is, in fact, rife with smallish bumps and crevices.
Further, we account for bumps and crevices by supposing that the stone is composed of much smaller things, molecules and so on, which are in such a combination that, while a large and sturdy stone is the upshot, no stone with a flat surface is found to obtain.The distinction sets up the foundation for the final argument of the paper: that knowledge requires certainty and that, certainty being an absolute term, it follows that it can never be achieved in reality.