For many years, my online signature block has included the title of this post (along with "all things are connected, therefore nothing is irrelevant" and "everything is relative - the only constant"). These thoughts were formed after several late-night hours of alcohol-fueled discussion on life and the nature of things. These may be the only absolute, unequivocal truths that there are. I do not claim to have originated these thoughts of course, just to have become aware of them. As might have been considered by the Beatles while writing one of there songs, there is nothing you can think that has not already been thought.
There are, of course, many other things that are true, but maybe not under all conditions and in all situations. Conditions and situations are things that vary, and thus are variables in determining the truth. It is impossible to test something or measure the truth under completely identical conditions. If nothing else, time is a variable that will NEVER be the same.
The truths I use in my online signature block are universal truths for all time. There may be others, and probably are. To be universal, the truth must hold up under all possible conditions, circumstances, and situations. To be for all time, the truth must have always been, and always will be.
These are fairly esoteric concepts and seem far removed from everyday life and human consciousness. But there are many more familiar concepts that come from the more esoteric concepts. I like the concept of perspective. None of us see the same exact colors, none of us have had the same exact experiences, and we all have different perspectives on everything. All things are relative (everything depends on your perspective).
We are all aware of the passage of time, because all things change. The sun moves, the hands on the clock change position, our bodies change, etc. In fact, the very concept of change requires the passage of time. The period of time that must pass for change to occur varies with whatever is changing.
The web of life, global warming, The Internet, the shrinking world, and many other similar concepts remind us on a daily basis that everything is connected, and nothing is irrelevant.
BB