This book is a slightly emended version of a dissertation presented at the University of Hull in 1972. I realise only too well the deficiencies of style, presentation and material which this involves. The title implies a more final note than I had intended in my treatment of Porphyry. On reflexion, however, it seemed the most suited to convey the general purpose of my enquiries. A more rounded assessment of Porphyry can come only after some more basic work has been completed. An edition of his philosophical fragments, to which I am now turning my attention, is a prerequisite. lowe, of course, a great deal to all those who have written on Neo- platonism. I am particularly indebted to Prof. Willy Theiler under whose guidance I studied in Bern. Conversation with him always resulted in new directions of enquiry and I was constantly stimulated by his breadth of knowledge. I must also thank Prof. A. H. Armstrong who has constantly encouraged me and helped me to look more deeply into a number of problems. Welcome, too, was a detailed criticism of Part Two by Dr. R. T. Wallis. Their criticism and advice have not always been followed and the responsibility for the faults and weak- nesses of this book rests on myself.