In earlier times people tried to use as criterion of chirality (or of optical activity, not differentiated then) the presence or absence of certain local features of molecular structure, the so-called elements of chirality:

• "Center of chirality" ("chiral center", "asymmetric center", in most cases an asymmetric carbon atom)
• "Axis of chirality" ("chiral axis")
• "Plane of chirality" ("chiral plane")

Today we know that such a procedure cannot work: Chirality of a macroscopic object is defined in exactly the same manner as of a molecule, therefore a criterion usable for molecular structures only cannot serve as a general criterion of chirality. In fact the presence of these structural features is neither sufficient for chirality, as shown above, nor necessary, as will be demonstrated below.

Axes and planes of chirality are neither easy to define nor easily observed. We therefore here are happy to do without such constructs, and instead derive chirality of a molecule as of a macroscopic object solely from its symmetry properties. This is all the more justified since by definition a complete molecule (a complete object) may be chiral or achiral, but not a point, a line or a plane in it.