  It is often claimed that the fundamental laws of physics are deterministic
and time-symmetric and that therefore our experience of the passage of time is
an illusion. This paper will critically discuss these claims and show that they
are based on the misconception that the laws of physics are an exact and
complete description of nature. I will argue that all supposedly fundamental
deterministic and time-symmetric laws have their limitations and are
supplemented by stochastic and irreversible elements. In fact, a deterministic
description of a system is valid only as long as interactions with the rest of
the world can be ignored. The most famous example is the quantum measurement
process that occurs when a quantum system interacts with a macroscopic
environment such as a measurement apparatus. This environment determines in a
top-down way the possible outcomes of the measurement and their probabilities.
I will argue that more generally the possible events that can occur in a system
and their probabilities are the result of top-down influences from the wider
context. In this way the microscopic level of a system is causally open to
influences from the macroscopic environment. In conclusion, indeterminism and
irreversibility are the result of a system being embedded in a wider context.
