# Quote — Werner Heisenberg, Physics and Philosophy

> The words "position" and "velocity" of an electron... seemed perfectly well defined... and in fact they were clearly defined concepts within the mathematical framework of Newtonian mechanics. But actually they were not well defined, as seen from the relations of uncertainty. One may say that regarding their position in Newtonian mechanics they were well defined, but in their relation to nature, they were not. This shows that we can never know beforehand which limitations will be put on the applicability of certain concepts by the extension of our knowledge into the remote parts of nature, into which we can only penetrate with the most elaborate tools. Therefore, in the process of penetration we are bound sometimes to use our concepts in a way which is not justified and which carries no meaning. Insistence on the postulate of complete logical clarification would make science impossible. We are reminded... of the old wisdom that one who insists on never uttering an error must remain silent.

- Author: [Werner Heisenberg](https://www.leafyquotes.com/werner-heisenberg.md)
- Book: [Physics and Philosophy](https://www.leafyquotes.com/werner-heisenberg/physics-and-philosophy.md)
- Source: [Wikiquote](https://en.wikiquote.org/wiki/Werner_Heisenberg#Physics_and_Philosophy_(1958)) ([CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/))
- Quote page: https://www.leafyquotes.com/werner-heisenberg/physics-and-philosophy/the-words-position

## More from this book

> But the resemblance of the modern views to those of Plato and the Pythagoreans can be carried somewhat further. The elementary particles in Plato's Timaeus are finally not substance but mathematical forms. "All things are numbers" is a sentence attributed to Pythagoras. The only mathematical forms available at that time were such geometric forms as the regular solids or the triangles which form their surface. In modern quantum theory there can be no doubt that the elementary particles will finally also be mathematical forms but of a much more complicated nature.

[Quote page](https://www.leafyquotes.com/werner-heisenberg/physics-and-philosophy/but-the-resemblance.md)

> The law of causality is no longer applied in quantum theory and the law of conservation of matter is no longer true for the elementary particles. Obviously Kant could not have foreseen the new discoveries, but since he was convinced that his concepts would be "the basis of any future metaphysics that can be called science" it is interesting to see where his arguments have been wrong.

[Quote page](https://www.leafyquotes.com/werner-heisenberg/physics-and-philosophy/the-law-of-causality.md)

> The equation of motion holds at all times, it is in this sense eternal, whereas the geometrical forms, like the orbits, are changing. Therefore, the mathematical forms that represent the elementary particles will be solutions of some eternal law of motion for matter. Actually this is a problem which has not yet been solved.

[Quote page](https://www.leafyquotes.com/werner-heisenberg/physics-and-philosophy/the-equation-of-motion.md)