Gerardus 't Hooft

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The axioms for any "complete" quantum theory for the entire cosmos would present us with as yet unresolved paradoxes.

Gerardus 't Hooft (born July 5, 1946) is a professor in theoretical physics at Utrecht University, the Netherlands. He shared the 1999 Nobel Prize in Physics with Martinus J. G. Veltman "for elucidating the quantum structure of electroweak interactions".


  • If you really want to contribute to our theoretical understanding of physical laws — and it is an exciting experience if you succeed! — there are many things you need to know. First of all, be serious about it!
  • On your way towards becoming a bad theoretician, take your own immature theory, stop checking it for mistakes, don't listen to colleagues who do spot weaknesses, and start admiring your own infallible intelligence.
  • The usual no-go theorems telling us that hidden variables are irreconcilable with locality, appear to start with fairly conventional pictures of particle systems, detectors, space and time. Usually, it is taken for granted that events at one place in the universe can be described independently from what happens elsewhere. Perhaps one has to search for descriptions where the situation is more complex. Maybe, it needs not be half as complex as superstring theory itself. The conventional Copenhagen interpretation of quantum mechanics suffices to answer all practical questions concerning conventional experiments with quantum mechanics, and the outcome of experiments such as that of Aspect et al can be precisely predicted by conventional quantum mechanics. This is used by some to state that no additional interpretation prescriptions for quantum mechanics are necessary. Yet we insist that the axioms for any "complete" quantum theory for the entire cosmos would present us with as yet unresolved paradoxes.
  • In practice, quantum mechanics merely gives predictions with probabilities attached. This should be considered as a normal and quite acceptable feature of predictions made by science: different possible outcomes with different probabilities. In the world that is familiar to us, we always have such a situation when we make predictions. Thus the question remains: What is the reality described by quantum theories? I claim that we can attribute the fact that our predictions come with probability distributions to the fact that not all relevant data for the predictions are known to us, in particular important features of the initial state.
  • When investigating theories at the tiniest conceivable scales in nature, almost all researchers today revert to the quantum language, accepting the verdict from the Copenhagen doctrine that the only way to describe what is going on will always involve states in HIlbert space, controlled by operator equations.
  • ... trying to solve a paradox will lead to new kinds of understanding. And I think that the problem of subjecting black holes to quantum mechanics is a fundamental paradox of the same nature, and the same depth, and the same importance as the paradox that Max Planck was studying at the beginning of the twentieth century.

Quotes about 't Hooft

  • Gerard is a Dutchman. The Dutch are the tallest people in Europe, but Gerard is short and solidly built, with a mustache and the look of a burgher. Like Feynman, 't Hooft has a strong competitive streak, but I am sure that I never got the better of him. Unlike Feynman, he is a product of old Europe — the last great European physicist, inheritor of the mantle of Einstein and Bohr. Although he is six years younger than I am, I was in awe of him in 1981, and rightfully so. In 1999 he was awarded the Nobel Prize for his work leading to the Standard Model of elementary particles.
    • Leonard Susskind, The Black Hole War (2008), p. 19
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