  The search for extraterrestrial intelligence (SETI) has been heavily
influenced by solutions to the Drake Equation, which returns an integer value
for the number of communicating civilisations resident in the Milky Way, and by
the Fermi Paradox, glibly stated as: "If they are there, where are they?". Both
rely on using average values of key parameters, such as the mean signal
lifetime of a communicating civilisation. A more accurate answer must take into
account the distribution of stellar, planetary and biological attributes in the
galaxy, as well as the stochastic nature of evolution itself. This paper
outlines a method of Monte Carlo realisation which does this, and hence allows
an estimation of the distribution of key parameters in SETI, as well as
allowing a quantification of their errors (and the level of ignorance therein).
Furthermore, it provides a means for competing theories of life and
intelligence to be compared quantitatively.
