 Then it is postulated that, for any \(f: \Delta \rightarrow \bR\), there is a unique \(D \in \bR\) such that equation (4) holds for all \(\varepsilon\). This says that the graph of \(f\) is a straight line passing through \((0, f\)(0)) with slope \(\Delta\). Thus any function on \(\Delta\) is what mathematicians term affine, and so this postulate is naturally termed the principle of microaffineness. It means that \(\Delta\) cannot be bent or broken: it is subject only to translations and rotations—and yet is not (as it would have to be in ordinary analysis) identical with a point. \(\Delta\) may be thought of as an entity possessing position and attitude, but lacking true extension.