When Plato, as the culmination of a long development in Greek thought, enunciated his theory of form, he exposed and brought to the fore one of the most profound of philosophical issues which, in one guise or another, has played a fundamental role in all subsequent philosophical thought. This issue is that of the nature and status of form, and of its relation to actuality . I use the term 'form' here in its most general connotation, and not with any restricted meaning such as might be attached to it by some particular theory of form ; so that the term covers also a nominalistic conception of form.