I have started 'Reality, Being and Existence: An Introduction to Metaphysics'. There are 36 people on the course, which is a good number and considerably more than on my previous two courses. Students come from all around the World, including DRC, which I think must be a first.
As part of the introduction I have been contemplating the concept of change.
Firstly, there seems to be a very close relationship between the idea of change and the idea of time. It seems that any definition of change needs to refer to or utilise the idea of time. I can't see any way of explaining change other than by using the concept of time. 'States of affairs being different at different times' is a simplistic way of defining change, but captures the essence of the concept.
I also think that the idea that time is bi-directional, we can talk about time moving forwards and time moving backwards. Times arrow shows us that time moves in one direction in the physical universe. This idea seems to be related to entropy. It is generally accepted that the universe displays entropy as a universal law, and that this entropy shows us the direction in which times arrow points.
The status of the arrow of time seems to be a fundamental metaphysical question. This leads to some fascinating ideas such as time travel and whether time has a beginning or end.