What is a Man? What is a Woman?

Most will assume that “male” and “female” are non-vague characteristics, and that is true much of the time; yet even biology can become vague and sex isn’t just a matter of what chromosomes you have. Socially, we don’t distinguish male from female based upon the genetic profile because we don’t have access to that. Instead, we take a look at their physical characteristics: do they look stereotypically female or male?

To what degree are we justified in using these markers for distinguishing male from female, though? Are they a reliable basis for social policy and for deciding who can marry whom? This won't be a problem for most couples, but a just social policy must be constructed so that the indeterminate cases are not treated unjustly. Deciding who can marry whom isn't always a simple matter of determining what sorts of internal organs a person has.