# Philip Warren Anderson

Philip Warren Anderson (December 13, 1923 – March 29, 2020) was an American theoretical physicist.

## Quotes

* The oxide superconductors, particularly those recently discovered that are based on La$_2$CuO$_4$, have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties. This insulating phase is proposed to be the long-sought "resonating-valence-bond" state or "quantum spin liquid" hypothesized in 1973. This insulating magnetic phase is favored by low spin, low dimensionality, and magnetic frustration. The preexisting magnetic singlet pairs of the insulating state become charged superconducting pairs when the insulator is doped sufficiently strongly.
** (6 Mar 1987)"The Resonating Valence Bond State in La$_2$CuO$_4$ and Superconductivity". Science 235 (4793): 1196–1198. DOI:10.1126/science.235.4793.1196.
* It is seen as the application of a systematic “scientific method” involving wearing a white coat and being dull. I feel that too many young people come into science with this view, and that too many fields degenerate into the kind of work which results: automatic crank-turning and data-collecting of the sort which Kuhn calls “normal science” and Rutherford “stamp-collecting”. In fact, the creation of new science is a creative act, literally, and people who are not creative are not very good at it.
** in Some ideas on the Aesthetics of Science, address presented by Philip W. Anderson as the Nishina Memorial Lecture at the 50th Anniversary Seminar of the Faculty of Science&Technology, at Keio University (Tokyo), on May 18, 1989.
* My belief is based on the fact that string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance.
** "God (or Not), Physics and, of Course, Love: Scientists Take a Leap". New York Times. 2005-01-04. Retrieved on 2006-08-22.
** Anderson was describing his dislike for "string theory".
* I learned, practically in my cradle (actually from Bill McMillan's thesis), that the ground state wave function of a system of bosons should necessarily be real and positive, a fact which made his early Monte Carlo simulations infinitely easier.
** (23 March 2018)"Four Last Conjectures". arXiv.org. (section on "Overlap Currents")

### More Is Different (1972)

* The behavior of large and complex aggregates of elementary particles, it turns out, is not to be understood in terms of a simple extrapolation of a few particles. Instead, at each level of complexity entirely new properties appear, and the understanding of the new behaviors requires research which I think is as fundamental in its nature as any other.
** p. 393 of (4 August 1972)"More is different". Science 177 (4047): 393–396.
* By symmetry we mean the existence of different viewpoints from which the system appears the same. It is only slightly overstating the case to say that physics is the study of symmetry. The first demonstration of the power of this idea may have been by Newton, who may have asked himself the question: What if the matter here in my hand obeys the same laws as that up in the sky—that is, what if space and matter are homogeneous and isotropic?
** p. 394
* ... the state of a really big system does not at all have to have the symmetry of the laws which govern it; in fact, it usually has less symmetry.
** p. 395
* Surely there are more levels of organization between human ethology and DNA than there are between DNA and quantum electrodynamics, and each level can require a whole new conceptual structure.
** p. 396

### More and Different: Notes from a Thoughtful Curmudgeon (2011)

* That Big Science culture in the USA, and similar groups elswhere, tended to have separate, direct access to government and hence to funding sources. It was independent to a great extent of the rest of science, of which it was never a majority component except in funding.
** p. 94
* “Of course I am not religious—I don’t in fact see how any scientist who thinks at all deeply can be so ...”
** p. 133
* All I can say to the younger theorists is: don’t trust anyone over 45, except maybe me, and I’m not so sure about me.”
** p. 159, quoted by N. David Mermin in (January 2012)"Review of More and Different: Notes from a Thoughtful Curmudgeon by Philip W. Anderson". Physics Today 65 (1). DOI:10.1063/PT.3.1400.
* My Harvard classmate, Thomas S. Kuhn wrote, some years ago, an influential book about scientific revolutions. Fortunately, many scientific revolutions do not follow his scenario, but the one he focused on, the discovery of quantum mechanics, is well described by his model, which is most valid for a revolution occurring in the central core of a mature science.
** p. 166
* “We atheists can . . . argue that, with the modern revolution in attitudes toward homosexuals, we have become the only group that may not reveal itself in normal social discourse”.
** p. 177