  In a recent paper, I argued against backward in time effects used by several
authors to explain delayed choice experiments. I gave an explanation showing
that there is no physical influence propagating from the present to the past
and modifying the state of the system at a time previous to the measurement.
However, though the solution is straightforward in the case of delayed choice
experiments involving only one particle, it is subtler in the case of
experiments involving two entangled particles because they give rise to
EPR-like situations. Considering that a measurement is not an actual change of
the physical state of a system and is relative to the observer allows to
understand that there is neither backward in time effects nor instantaneous
collapse of the second system when the first one is measured, as is often
postulated.This allows also to get rid of any non-locality. In this paper, I
want to go further into the consequences of this way of considering the
measurement, that I have called Convivial Solipsism, and show that even if, in
the usual sense, there is no physical effect of the present or of the future on
the past, we must nevertheless consider that the observer's past is sometimes
not entirely determined and that it becomes determined only when certain
measurements are done latter. This apparent contradiction disappears if one
understand that each observer builds, through her own measurements, her own
world (that I call the phenomenal world in Convivial Solipsism) which is
different from what we are used to consider as the common world shared by
everybody.
