It is generally believed 

that our science is empirical 

and that we draw our concepts 

and our mathematical constructs 

from the empirical data. 

If this were the whole truth, 

we should, when entering into a new field, 

introduce only such quantities 

as can directly be observed, 

and formulate natural laws 

only by means of these quantities.

The uncertainty relation does not refer to the past; 

if the velocity of the electron is at first known 

and the position then exactly measured, 

the position for times previous to the measurement may be calculated.

Whoever dedicates his life to searching out particular connections of nature 

will spontaneously be confronted with the question 

how they harmoniously fit into the whole.

Every word or concept, 

clear as it may seem to be, 

has only a limited range of applicability.

Separation of the observer
from the phenomenon to be observed
is no longer possible.

The reality we can put into words is never reality itself.

What we observe is not nature itself, 

but nature exposed to our method of questioning.

Natural science, does not simply describe and explain nature; 

it is part of the interplay between nature and ourselves.