  This is a short text covering some topics on the Foundations of Quantum
Theory and it includes some comments on the recent Nature article by D.
Frauchiger and R. Renner. The so-called "paradox" is simply due to a
misunderstanding on the appropriate way to apply the quantum mechanical rules.
The text is meant to be accessible to non physicists and the math is kept to a
minimum (just some Linear Algebra and extremely elementary Probability Theory).
