The Original of Albert Einstein’s Widely Published Answer to the Detractors of Relativity, Stating That Their Common Sense Is As Much a Construct as Relativity

"Common sense invents and constructs no less in its own field than science does in its domain.  It is, however, in the nature of (naive) common sense not to be aware of this situation.”

In 1905, while a young patent clerk and physicist in Bern, Switzerland, Albert Einstein obtained his doctorate and published a paper that explained his newly developed Special Theory of Relativity. This unlocked many mysteries of the universe, and introduced the world to "e=mc2," equating mass and the speed of light with energy.  It established that time and space are not fixed, and in fact change to maintain a constant speed of light regardless of the relative motions of sources and observers. Just 10 years later, in 1915, Einstein published his General Theory of Relativity, which described the universe as a four-dimensional continuum (with time added as the fourth dimension), where gravitational effects are explained by the warping of space-time.  In this theory, Einstein incorporated gravity as a geometric property of space-time.

In 1921, Einstein won the Nobel Prize for his groundbreaking work, and Time Magazine named him the Person of the Century for the 20th century for his discoveries in relativity and space-time. Einstein is the most important scientist since Isaac Newton, and probably the most famous in history.

Einstein's relativity theories challenged many principles of physics that had been accepted for centuries, and specifically supplanted many of the assumptions of Newtonian physics.  It required a fundamental shift in the way people viewed the world around them, and not everybody was ready to accept that. Einstein had his detractors and opponents, people who claimed that relativity could not be true because it violated their obvious perceptions. So at the heart of the opposition to Einstein was a principle called "naive common sense." This is the way in which we interact with our physical surroundings.  Our rational mind sees things and assumes they are what they claim to be.  They appear to be as they are.  I see something going at a particular speed and it is in fact appearing to go at that speed. Relatively challenged that.  How could that be – things appearing different to different observers, which is the essence of relativity?

In fact, the initial reaction of this "naive common sense" is to assume that relativity must be incorrect.  Einstein considered this type of common sense to be a collection of prejudices. That he rejected this form of "common sense”, and classical principles of motion, goes to the heart of his definitions of space and time, and his rejection of absolute time and absolute space.  The pre-Einstein definition of "absolute rest," for instance, requires a corresponding definition of absolute space in relation to it, and he rejects this, demonstrating empirically that such things are measured in relation to other objects, hence relativity.  He does not reject entirely the notion of common sense – he simply states that it is not the fixed, reliable perspective through which all must be true.

This distinction cuts at the heart of what made Relativity so revolutionary.  It draws a line in the sand between the work of Einstein and his predecessors, and defines how we view space and time today.  It represents a fundamental change from the worldview of Newtonian physics.

In 1951, Einstein wrote a woman a letter in which he challenged how we view things in our every day perceptions, making the point that common sense cannot be taken at face value, as even what we perceive to be true might be a figment.  And although it is true that science must invent, so must our every day perceptions; yet we are unaware of the perceptions being invented.  That letter is now famous, and the quotation is among Einstein's great and simple statements, applying both to every day life and, for him, specifically to Relativity.

This is the original letter containing that important, and famous, statement.

Typed letter signed, on his blind embossed letterhead, Princeton, August 21, 1951, to Beatrice Bodenstein.  "Dear Miss Bodenstein: Common sense invents and constructs no less in its own field than science does in its domain.  It is, however, in the nature of (naive) common sense not to be aware of this situation.  Sincerely yours, A. Einstein.” This quotation has been cited innumerable times in publications, both in print and online.

Letters of Einstein in which he coined well-known quotations very rarely reach the market, this being just the second or third we have had in our three decades in the field. That it constitutes his answer to the detractors of relativity makes it all the more significant.