Authorship analysis is the process of determining who produced a
questioned text by language analysis. Although there has been
significant success in the performance of computational methods to solve
this problem in recent years, these are often methods that are not
amenable to interpretation. Authorship analysis is in all effects an
area of computer science with very little linguistics or cognitive
science. This Element introduces a Theory of Linguistic Individuality
that, starting from basic notions of cognitive linguistics, establishes
a formal framework for the mathematical modelling of language processing
that is then applied to three computational experiments, including using
the likelihood ratio framework. The results propose new avenues of
research and a change of perspective in the way authorship analysis is
currently carried out.