Reality is overrated

(This began as a reply post in a google group (like a usenet group).)

There's no one absolute dividing line between "real" and "imaginary".  Anything you imagine is real and significant if you care about it.  

(Example:  If you have a vivid dream in which you feel emotion, that is a real experience, whether you remember it later or not.  Some people not only remember their dreams, but can also be aware that they are dreaming, while they are dreaming.  And some people can re-enter their dreams.  It's plausible to suppose that the reality within a dream is significant, as reality, and just as significant as what's real when you're "awake".  The more you care about a thing, the more _significant_ it is, to you and to anyone else who cares about it, whether anyone wants to call it "real" or not.  And that significance may be more important or relevant than whether it matches anyone else's definition of what's real or not.)

Yes we have a convention of 3 spatial dimensions and 1 time dimension but you can also add dimensions such as color or heat, or all the dimensions of a suit of clothes ("measurements" of the human body -- relevant when buying a suit).  I think the convention of 3 spatial dimensions and 1 time dimension is actually arbitrary but we cannot see through that illusion.  

Rather than count dimensions and define physical reality for all, it's usually better to adopt systems that are _useful_, while realizing that there may be _other_ systems that are useful in other ways!  

For example a spherical geometry is useful in navigating on a planet, and in such a system, it may make more sense for "parallel" lines to meet in the distance rather than be forever equidistant for each other.  There's a certain arbitrariness to these systems and utility is usually a good criterion for choosing a system for some purpose.

For the most part, I think it's just fine to accept the 3 plus 1 dimensional physical reality as a useful convention, while realizing that it could ultimately be less than the whole of reality.  

As for imaginary numbers, yes the reality of those is kind of confusing but we can accept it as a convention and go with the flow.  If you make up any set of numbers and get enough people to agree on it, you can use that system and call it real.  Nobody is the final arbiter of what's real and what's not.

-jrl