Principles of Research

Albert Einstein

Physical Society, Berlin, 1918

IN the temple of science are many mansions, and various indeed are they that dwell therein and
the motives that have led them thither. Many take to science out of a joyful sense of superior
intellectual power; science is their own special sport to which they look for vivid experience and
the satisfaction of ambition; many others are to be found in the temple who have offered the
products of their brains on this altar for purely utilitarian purposes. Were an angel of the Lord to
come and drive all the people belonging to these two categories out of the temple, the
assemblage would be seriously depleted, but there would still be some men, of both present and
past times, left inside. Our Planck is one of them, and that is why we love him.
I am quite aware that we have just now lightheartedly expelled in imagination many excellent
men who are largely, perhaps chiefly, responsible for the buildings of the temple of science; and
in many cases our angel would find it a pretty ticklish job to decide. But of one thing I feel sure:
if the types we have just expelled were the only types there were, the temple would never have
come to be, any more than a forest can grow which consists of nothing but creepers. For these
people any sphere of human activity will do, if it comes to a point; whether they become
engineers, officers, tradesmen, or scientists depends on circumstances. Now let us have another
look at those who have found favor with the angel. Most of them are somewhat odd,
uncommunicative, solitary fellows, really less like each other, in spite of these common
characteristics, than the hosts of the rejected. What has brought them to the temple? That is a
difficult question and no single answer will cover it. To begin with, I believe with Schopenhauer
that one of the strongest motives that leads men to art and science is escape from everyday life
with its painful crudity and hopeless dreariness, from the fetters of one’s own ever shifting
desires. A finely tempered nature longs to escape from personal life into the world of objective
perception and thought; this desire may be compared with the townsman’s irresistible longing to
escape from his noisy, cramped surroundings into the silence of high mountains, where the eye
ranges freely through the still, pure air and fondly traces out the restful contours apparently built for eternity.
With this negative motive there goes a positive one. Man tries to make for himself in the fashion
that suits him best a simplified and intelligible picture of the world; he then tries to some extent
to substitute this cosmos of his for the world of experience, and thus to overcome it. This is what
the painter, the poet, the speculative philosopher, and the natural scientist do, each in his own
fashion. Each makes this cosmos and its construction the pivot of his emotional life, in order to
find in this way the peace and security which he cannot find in tbe narrow whirlpool of personal
What place does the theoretical physicist’s picture of the world occupy among all these possible
pictures? It demands the highest possible standard of rigorous precision in the description of
relations, such as only the use of mathematical language can give. In regard to his subject matter,ഊon the other hand, the physicist has to limit himself very severely: he must content himself with describing the most simple events which can be brought within the domain of our experience;
all events of a more complex order are beyond the power of the human intellect to reconstruct with the subtle accuracy and logical perfection which the theoretical physicist demands. Supreme
purity, clarity, and certainty at the cost of completeness. But what can be the attraction of getting to know such a tiny section of nature thoroughly, while one leaves everything subtler and more complex shyly and timidly alone? Does the product of such a modest effort deserve to be called by the proud name of a theory of the universe?

In my belief the name is justified; for the general laws on which the structure of theoretical
physics is based claim to be valid for any natural phenomenon whatsoever. With them, it ought
to be possible to arrive at the description, that is to say, the theory, of every natural process,
including life, by means of pure deduction, if that process of deduction were not far beyond the
capacity of the human intellect. The physicist’s renunciation of completeness for his cosmos is
therefore not a matter of fundamental principle.
The supreme task of the physicist is to arrive at those universal elementary laws from which the
cosmos can be built up by pure deduction. There is no logical path to these laws; only intuition,
resting on sympathetic understanding of experience, can reach them. In this methodological
uncertainty, one might suppose that there were any number of possible systems of theoretical
physics all equally well justified; and this opinion is no doubt correct, theoretically. But the
development of physics has shown that at any given moment, out of all conceivable
constructions, a single one has always proved itself decidedly superior to all the rest. Nobody
who has really gone deeply into the matter will deny that in practice the world of phenomena
uniquely determines the theoretical system, in spite of the fact that there is no logical bridge
between phenomena and their theoretical principles; this is what Leibnitz described so happily as
a “pre-established harmony.” Physicists often accuse epistemologists of not paying sufficient
attention to this fact. Here, it seems to me, lie the roots of the controversy carried on some years
ago between Mach and Planck.
The longing to behold this pre-established harmony is the source of the inexhaustible patience
and perseverance with which Planck has devoted himself, as we see, to the most general
problems of our science, refusing to let himself be diverted to more grateful and more easily
attained ends. I have often heard colleagues try to attribute this attitude of his to extraordinary
will-power and discipline — wrongly, in my opinion. The state of mind which enables a man to
do work of this kind is akin to that of the religious worshiper or the lover; the daily effort comes
from no deliberate intention or program, but straight from the heart. There he sits, our beloved
Planck, and smiles inside himself at my childish playing-about with the lantern of Diogenes. Our
affection for him needs no threadbare explanation. May the love of science continue to illumine
his path in the future and lead him to the solution of the most important problem in present-day
physics, which he has himself posed and done so much to solve. May he succeed in uniting
quantum theory with electrodynamics and mechanics in a single logical system.

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