Nature allows only experimental situations to occur which can be described within the framework of the formalism of quantum mechanics
Werner HeisenbergThe existing scientific concepts cover always only a very limited part of reality, and the other part that has not yet been understood is infinite.
Werner HeisenbergThus, the more precisely the position is determined, the less precisely the momentum is known, and conversely.
Werner HeisenbergIt is probably true quite generally that in the history of human thinking the most fruitful developments frequently take place at those points where two different lines of thought meet. These lines may have their roots in quite different parts of human nature, in different times or different cultural environments or different religious traditions: hence if they actually meet, that is, if they are at least so much related to each other that a real interaction can take place, then one may hope that new and interesting developments may follow.
Werner HeisenbergThe incomplete knowledge of a system must be an essential part of every formulation in quantum theory. Quantum theoretical laws must be of a statistical kind. To give an example: we know that the radium atom emits alpha-radiation. Quantum theory can give us an indication of the probability that the alpha-particle will leave the nucleus in unit time, but it cannot predict at what precise point in time the emission will occur, for this is uncertain in principle.
Werner Heisenberg