Bohr expressed in Light and Life (1933) the Thantalogical Principle stating that to check out the nature of something, one has to destroy that very nature, which we refer to as The Torturer's Dilemma:
- We should doubtless kill an animal if we tried to carry the investigations of its organs so far that we could describe the role played by single atoms in vital functions. In every experiment on living organisms, there must remain an uncertainty as regards the physical conditions to which they are subjected…the existence of life must be considered as an elementary fact that cannot be explained, but must be taken as a starting point in biology, in a similar way as the quantum of action, which appears as an irrational element from the point of view of classical mechanics, taken together with the existence of the elementary particles, forms the foundation of atomic physics.
- It has turned out, in fact, that all effects of light may be traced down to individual processes, in which a so-calles light quantum is exchanged, the energy of which is equal to the product of the frequency of the electromagnetic oscillations and the universal quantum of action, or Planck's constant. The striking contrast between this atomicity of the light phenomenon and the continuity of of the energy transfer according to the electromagnetic theory, places us before a dilemma of a character hitherto unknwown in physics.
- Planck's discovery of the universal quantum of action which revealed a feature of wholeness in individual atomic processes defying casual description in space and time.
- Planck's discovery of the universal quantum of action taught us that the wide applicability of the accustomed description of the behaviour of matter in bulk rests entirely on the circumstance that the action involved in phenomena on the ordinary scale is so large that the quantum can be completely neglected. (The Connection Between the Sciences, 1960)