Jade,
Let me re-phrase to avoid that interpretation of ‘boundary’.
Infinity is simply something that does not have a limit.
If there was a point where nothing existed then there could be no cause for anything to begin. Therefore something must have always existed. I.e. something must have the property of infinity.I don't see how the assertion that something infinite must exist in order for the universe to be here can be justified.
If it closed then it does have a boundary otherwise it could not be defined as closed.Let's take a closed universe, for example. It has no boundary, but it is not infinite.
Let me re-phrase to avoid that interpretation of ‘boundary’.
Infinity is simply something that does not have a limit.