>>13687802In seriousness, what I mean is that ?s > 0 is the correct relation. As an infinitesimally small quantity, it's close to 0 but not equal to 0.
Now, if you think of a number, say 42, on the number line, we can do 42 + ?s to move slightly to the right and 42 - ?s to move slightly to the left. In other words, we don't lose anything by insisting ?s be positive.
