not feel like the wanderer who was unable to see the forest for the
trees. May the book bring some one a few happy hours of suggestive
thought!

December, 1916
A. EINSTEIN



PART I

THE SPECIAL THEORY OF RELATIVITY

PHYSICAL MEANING OF GEOMETRICAL PROPOSITIONS


In your schooldays most of you who read this book made acquaintance
with the noble building of Euclid's geometry, and you remember --
perhaps with more respect than love -- the magnificent structure, on
the lofty staircase of which you were chased about for uncounted hours
by conscientious teachers. By reason of our past experience, you would
certainly regard everyone with disdain who should pronounce even the
most out-of-the-way proposition of this science to be untrue. But
perhaps this feeling of proud certainty would leave you immediately if
some one were to ask you: "What, then, do you mean by the assertion
that these propositions are true?" Let us proceed to give this
question a little consideration.

Geometry sets out form certain conceptions such as "plane," "point,"
and "straight line," with which we are able to associate more or less