  The aim of this work is to show how Einstein's quantum hypothesis leads
immediately and necessarily to a departure from classical mechanics. First we
note that the classical description and predictions are in terms of idealized
measurements that are exact, instantaneous, non-perturbative, independent of
each other and process agnostic. If we assume we cannot arbitrarily reduce the
strength of a signal, measurements are ultimately perturbative to some degree.
We show how a physical description in which the best measurement conceivable,
i.e. the ideal measurement, perturbs the system leads to all the concepts
present in quantum mechanics including conjugate variables, probabilistic
predictions and measurements connected to symmetries.
