The Videotape

“Knowledge or Certainty” is an episode in the 1973 BBC series “The Ascent of Man,” a history of science from the prehistoric period to modern times. Although it shows its age a bit (smaller particles than that shown have been “photographed” since and the sexist title of the original series would probably be changed to something like “The Ascent of Humanity” today), most of it is still scientifically valid.

Jacob Bronowski (born 1908) emigrated with his family from Poland to Germany to England, where he studied mathematics at Cambridge University. During World War II, his work helped to increase the effectiveness of bombing raids. This connection led him to Nagasaki after the war to study the effects of the atomic bombing there, but he came away convinced that scientists needed to pay more attention to the ethics of science, and in particular the danger that their discoveries would be misused. This episode of “The Ascent of Man” concentrates on two catastrophic events of the 20th century for which scientists have often been blamed: the Nazi genocide of the Jews and the atomic bombings of Hiroshima and Nagasaki.

However, we are viewing this film for a slightly different reason. The defense of science which Bronowski mounts depends on the “uncertainty principle,” or “indeterminacy” or–as he prefers–“the principle of tolerance.” His insistence that there is no absolute truth, not even in science, descends from the same line of reasoning as Voltaire’s insistence on the limits of knowledge. Both argue that the logical result of human limitations should be tolerance.

The Science

You do not have to understand modern atomic physics to follow his argument, but it helps. He begins the film by focusing a number of devices on the face of an unnamed elderly man to see how much detail each can produce. The point of this exercise is to demonstrate that all perception, including that provided by scientific investigation, is necessarily imperfect, limited. Some aspects of our knowledge of this man which cannot be conveyed by scientific instruments can be conveyed instead by an artist trying to convey the man’s spirit or by a blind woman actually touching the man’s face. Watch for this man’s face to return at the very end of the film in the context of another reference to “touch.”

It is crucial to understand that he is not saying that there is no such thing as knowledge, or that all approaches to knowledge are equal. He emphasizes that we can be very precise about what we can and cannot know through scientific means. That in itself is important knowledge. But all knowledge is limited, never absolute. Philosophers and other humanists have often seized on uncertainty theory and quantum physics to argue for skepticism, and tried to use it to deny all validity to science. Why this is unjustified in most scientists’ opinion is beyond the scope of these modest notes, but it is important to keep in mind that Bronowski does believe in scientific knowledge: he simply denies that it is complete or perfect.

His references to “the knowledge of gods” may mislead some into thinking that he is claiming that such knowledge exists. Not at all. Later in the film he specifically asserts that there is no such knowledge. Lurking in the background of his argument is the same anti-religious message that Voltaire is advancing in The Philosophical Dictionary. When he says “dogma,” think “religious belief” as well as “racist theories.” In order not to offend and distract his audience, Bronowski downplays this aspect of his argument. According to this view, the limitations of science provide no justification for religion to claim superior “knowledge,” for religion is much more subjective and inexact than science.

His use of the word “tolerance” may be unfamiliar to you if you have not studied engineering. Parts are often manufactured to a certain degree of tolerance in the sense that a bolt may measure .25 centimeters give or take 15 millimeters. The “give or take” part is the “tolerance.” It is not possible to make anything to perfect dimensions–not just because of human imperfection, but because of uncertainties built into the very nature of matter. Bronowski is punning on this meaning of “tolerance” to connect it with the more common use of the term to express open-mindedness. Note how his analysis of science emphasizes that it progresses through questioning and argumentation, refusal to accept any finding as the last word. For him, science which becomes dogma is not science.

He rejects the term “uncertainty” because we are certain about what we cannot know in subatomic physics, and can even measure precisely the “tolerance” within which our knowledge is bounded.


Listed in the order in which they appear in the film.

Karl Friedrich Gauss German mathematician, 1777-1855.

University of Göttingen, founded 1737.

Ceres. Strictly speaking, not a planet but an asteroid, but the distinction is irrelevant for the period Bronowski is talking about. True planets discovered after the classical seven (which included the Sun and Moon): Uranus (1781), Neptune (1846) and Pluto (1930, though some now dispute whether Pluto should be classed as a true planet). Of course we now class the Earth itself as a planet, which the ancients did not.

Friedrich Hegel German philosopher who argued humans are capable of absolute knowledge based on reason, 1770-1831. Karl Marx was an important student and critic of Hegel’s work, and the Nazis tried to use him to justify their own ideology.

German unification. Germany was created as a modern state through a long process during the 19th century.

Max Born, German physicist, 1882-1970.

Werner Heisenberg, German physicist, 1901-1976. Student of Born. The “Heisenberg uncertainty principle” is named after him.

Erwin Schrödinger, Austrian physicist, 1887-1961.

Louis de Broglie, French physicist, 1892-1987.

Max Planck, German physicist, 1858-1947.

Johann Friedrich Blumenbach, German physiologist and comparative anatomist, 1752-1840.

Note: most of the refugees in the following group were Jews.

Albert Einstein, German physicist, 1879-1955. Renounced his citizenship and fled Germany in 1933. Settled in the U.S.

Sigmund Freud, Austrian psychiatrist, founder of psychoanalysis, 1856-1939. Fled Hitler’s Nazis when they invaded Austria in 1938 to seek refuge in England.

Bertolt Brecht, German playwright, 1898-1956. Fled Germany in 1933 for exile in Denmark and the U.S. Later fled the U.S. to escape anti-Communist persecution and had a notable career and a Communist playwright in East Germany.

Arturo Toscanini, Italian conductor, 1867-1957. Avoided Fascist Italy and Nazi Germany, settling in 1937 in the U.S., where he conducted the NBC Symphony, created for him.

Bruno Walter, German conductor, 1876-1962. Fled Germany for Austria in 1936, then on to Paris, and finally settled in the U.S. in 1939.

Marc Chagall, Belorussian painter, 1887-1985. Fled Germany in 1939 for France.

Enrico Fermi, Italian physicist, 1901-1954. Fled Fascist Italy in 1938 for the U.S. Fermi headed the Chicago portion of the Manhattan Project, the project to build the atomic bomb. He became an American citizen in 1944.

Leo Szilard, Hungarian physicist, 1898-1964. Fled Gerany in 1933 for Austria, then London, and–in 1937–the U.S. Helped Fermi design the first nuclear reactor. Like many in Chicago who had joined the project mainly to defeat Hitler, he objected to its planned use against the Japanese, particularly since they were not to be warned in advance. He dedicated much of the rest of his life to working against nuclear weapons.

Salk Institute of Biological Studies, La Jolla, California. Founded in 1963 by U.S. medical researcher Jonas Salk, most famous for his development of the first effective polio vaccine.

Arbeit macht frei “Work makes one free.” The notoriously ironic motto over the gate at the Auschwitz (Oswiecim, Poland) death camp. Shown are the gas ovens where the corpses of gassed Jews and other victims were incinerated, and the collection of glasses destined for “recycling.”

Oliver Cromwell, Puritan leader of the revolution which overthrew Charles I. His famous plea, “I beseech ye in the bowels of Christ, think that ye may be mistaken,” was made to his Scottish opponents just before he defeated them in the Battle of Dunbar (1650); but is often cited in defense of open-mindedness generally. “Bowels” here means something like “heart,” as used in the King James translation of Philemon.

More study guides for 18th and 19th Century European Classics


Auschwitz Alphabet
Louis de Broglie
Albert Einstein
Enrico Fermi
Werner Heisenberg
Max Planck
The Salk Institute
Erwin Schödinger


What do you find most interesting or persuasive about this film?

What are the strong and weak points of Bronowski’s argument that science itself is not responsible for the purposes to which it is put by politicians?

Compare what he is saying about the limits of knowledge with what Voltaire has to say about the same subject.

What does Bronowski mean when he says “We have to reach out and touch people”?

Why was the elderly man we saw at the beginning of the film an appropriate choice?