I entered Princeton University as a graduate student in 1959, when the Department of Mathematics was housed in the old Fine Hall. This legendary facility was marvellous in stimulating interaction among the graduate students and between the graduate students and the faculty. The faculty offered few formal courses, and essentially none of them were at the beginning graduate level. Instead the students were expected to learn the necessary background material by reading books and papers and by organising seminars among themselves. It was a stimulating environment but not an easy one for a student like me, who had come with only a spotty background. Fortunately I had an excellent group of classmates, and in retrospect I think the "Princeton method" of that period was quite effective.

... was wonderfully supportive and enthusiastic and his guidance made an enormous impact on my mathematical career. I remember well that a couple of mornings a week I would go to his office to present material to him. In those sessions I learned, among other things, Lie groups, sheaf cohomology, complex manifolds and differential geometry (the equivalence of the then-existing seven definitions of a connection).

This turned out to be the beginning of a personal and professional relationship that has lasted for more than forty years.

Though the papers selected cover a broad range of topics in complex analysis, algebraic geometry and differential equations ... there are a couple of fundamental threads running through things, over and above the stylistic and methodological outlook. Many of the papers return to the idea of examining geometric behaviour infinitesimally, in families of one sort or another, and trying to integrate the local results out to obtain global results, with varying degrees of success, of course. Some of the author's most enduring results come from simple such calculations which show how different higher-dimensional variations of cycles or Hodge structures are, often referred to as Griffiths transversality. This implies in various guises that, e.g., numerical equivalence and algebraic equivalence of cycles on projective varieties are different, that not every Hodge structure can be realized geometrically, and in a way, his proof with Clemens of the irrationality of the quartic threefold is at bottom a phenomenon of this sort. This sort of observation leads directly into the use of the exterior differential systems of Élie Cartan to try to find the "geometric core", e.g., of the moduli space of Hodge structures, which led to a great deal of the author's work in the early 1980s, and which spun off into the examination of PDE invariants via the exterior differential systems in the 1990s.

Certainly to a greater degree than other mathematicians of his standing, he has often opted for writing in a way that was expository, sometimes for his audience, but sometimes even for himself .... He writes ... of his conviction that one could learn as much or more from a clear proof or calculation in an insightful example or a meaningful case, as from a proof of the most general case one is capable of proving. ... At times [Griffiths] refers to the style of a paper as an "essay", allowing for a more discursive treatment of his subject. He even refers to the 1976 paper "Variations on a theme of Abel" as "the mathematical analogue of a historical novel"!

This book is a model of serious expository writing. ... Results are sometimes stated under mildly restrictive hypotheses in order to have clean statements, and technical details are often omitted. This makes for a crisp, attractive presentation.

Phillip has been an exceptionally effective Director of the Institute since 1991, and he will be greatly missed. We all have enormous respect for him personally and for his accomplishments. His tenure has been marked both by his ability to guide this institution in productive and exciting new directions, and his ability to further strengthen the unique opportunities the Institute offers to scholars from all over the world. ... Griffiths served as a key figure in the creation in 1998 of the Millennium Science Initiative [which] works to strengthen the science and technology capacity of developing nations through integrated projects of research and training planned and driven by local scientists. Currently, initiatives in Chile, Brazil, and Mexico are underway, and initiatives are being planned in sub-Saharan Africa and Vietnam.