2. The argument so far has glossed over the question of fluctuations. It has also implicitly assumed that the uncertainty predicted at time t 1 for the variables at time t 2 will be much smaller than the measurement error. But if the measurements do meaningfully update our knowledge of the system, our uncertainty as to its state is reduced, giving a new S I which is less than S I. (Note that if we allow ourselves the abilities of Laplace's demon, the consequences of this new information can also be mapped backwards, so our uncertainty about the dynamical state at time t 1 is now also reduced from S I to S I).