The present book originates from my Ph.D. thesis, a critical survey of attempts to determine the order of composition of Plato's works by analysing their style, which has been brought up to date by the inclusion of two investigations carried out since that time. On the other hand, several investigations in the thesis have now been omitted, as they seemed to be of only slight significance. The idea of including an account of research on questions of authenticity was rejected as likely to lead to a volume of increased complexity and unmanageable proportions; although closely connected with the problem of chronology, that of authorship provides sufficient material to justify separate treatment.

In a work of this nature the accuracy of the statistics is of paramount importance, and the opportunity has been taken to check them, wherever feasible, with the Word Index which is now available. It should be remembered, however, that this relates to Burnet's Oxford text, which did not exist when most of the research described was carried out, so that some statistical discrepancies may have arisen from different textual readings rather than from careless observation. Nevertheless, as anyone will know who has tried to record by hand the incidence of words or phrases in a text, complete accuracy is almost impossible to attain, and the fact that checks generally revealed only small errors is a tribute to the painstaking diligence and dedication of the scholars concerned.